NOVA GORICA POLYTECHNIC SCHOOL OF ENVIRONMENTAL SCIENCES

GRADUATE STUDY PROGRAMME OF ENVIRONMENTAL SCIENCES

Gregor JEREB

BIODEGRADABLE MUNICIPAL SOLID WASTE MANAGEMENT

SEMINAR WORK

Modern trends in environmental sciences

Nova Gorica, 2004

Jereb, G. Biodegradable municipal solid waste management. II Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 KEY WORD DOCUMENTATION CX: biowaste/municipal solid waste/composting/digestion AU: JEREB, Gregor, B.Sc. in Sanitary Engineering PY: 2004 TI: BIODEGRADABLE MUNICIPAL SOLID WASTE MANAGEMENT DT: Seminar work NO: VI, 22 p., 1 tab., 6 fig., 20 ref. AB: Municipal, industrial and agricultural solid waste and biomass deposits cause large scale pollution of land, air and water. A large amount of municipal waste represent organic fraction. All biodegradable wastes can be treated with processes of bioconversion in facilities using advanced technology. Regulating and speeding up natural biological processes can be one of the steps to achieve an optimal system for processing organic waste. Also European Council Landfill Directive (1999/31/EC) was adopted to solve collection and processing of biodegradable waste in member states. Composting will have an important role in processing much of the biodegradable waste, which in future will have to be diverted from landfill. All kind of organic fraction of municipal solid waste are appropriate for composting. Even better results can be achieved with mixtures different fraction of organic waste, so we can assure easy handling of the materials during operation, reduction of odor emission, less need is for C/N ratio correction and moisture adding, and also operating time is decreased. For treatment of biological waste we can serve different techniques. Most common are composting, anaerobic decomposition and fermentation. Different variety of this techniques, and also compost usage are describes in seminar.

Jereb, G. Biodegradable municipal solid waste management. III Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 TABLE OF CONTENTS

KEY WORD DOCUMENTATION ............................................................................ II TABLE OF CONTENTS.............................................................................................III LIST OF FIGURES ..................................................................................................... IV LIST OF TABLES .........................................................................................................V ABBREVIATIONS ...................................................................................................... VI

1 INTRODUCTION.......................................................................................................... 1

2 EUROPEAN COUNCIL DIRECTIVE ON THE LANDFILL OF WASTE............ 4

3 COMPOST POTENTIAL OF ORGANIC FRACTION OF SOLID WASTE......... 5

4 BIOLOGICALLY BASED METHODS FOR MANAGEING ORGANIC WASTE6

4.1 CODIGESTION OF MUNICIPAL SOLID WASTE AND BIOSOLIDS............... 6

4.2 PH AND TEMPERATURE REGULATION CONTROL METHOD .................... 7

4.3 DECOMPOSITION OF FOOD WASTE............................................................... 10

4.4 VERMICOMPOSTING MUNICIPAL SOLID WASTE WITH EARTHWORMS10

5 BIOGAS AND COMPOST ......................................................................................... 12

5.1 PRODUCTION OF BIOGAS AND COMPOST BY MIXING AEROBIC/ANAEROBIC CONDITIONS......................................................................... 12

5.2 METHANE PRODUCTION.................................................................................. 13

5.3 HYDROGEN PRODUCTION FROM ORGANIC WASTE................................. 14

5.4 COMPOST USAGE............................................................................................... 16

5.5 SOURCES OF HEAVY METALS IN BIOWASTE COMPOST ......................... 17

5.6 COMPOST USING AS A LANDFILL CLOSURE CAPS ................................... 18

6 CONCLUSIONS........................................................................................................... 19

7 SUMMARY................................................................................................................... 21

8 REFERENCES ............................................................................................................. 22

Jereb, G. Biodegradable municipal solid waste management. IV Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 LIST OF FIGURES Figure 1.1: Municipal waste collected in selected countries in WE, CEE and EECCA (Okolje

Evrope: Tretja presoja, Zbirno poročilo 2003: 42) ............................................................ 2 Figure 4.1: A simplified description of the compost reactor, indicating where CO2, O2,

temperature and pH in compost material and condensed liquid were measured (Smars et al., 2002: 238)..................................................................................................................... 8

Figure 4.2: The cumulative CO2–C emissions of the 3 + 3 Regime I and II runs (Smars et al., 2002: 240) .......................................................................................................................... 9

Figure 5.1: Biogas volume in alternative sequences of batch aerobic and anaerobic processes (Krzystek et al., 2001: 109).............................................................................................. 13

Figure 5.2: Schematic diagram of experimental aparatures, (Nielsen et al., 2001: 548) ......... 15 Figure 5.3: Hydrogen concentration as a function of time during the fermentation in the

bioreactor (□), and both before (∆) and after (*) the Pd/Ag membrane (Nielsen et al., 2001: 549) ........................................................................................................................ 16

Jereb, G. Biodegradable municipal solid waste management. V Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 LIST OF TABLES Table 4.1: Time taken to reach different levels (10%, 20%, 30%, 40%, 45% of initial C) of

cumulative CO2–C emissions in days (Smars et al., 2002: 240) ....................................... 9

Jereb, G. Biodegradable municipal solid waste management. VI Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 ABBREVIATIONS MSW – municipal solid waste OFMSW – organic fraction of municipal solid waste TOC – total organic carbon DOC – dissolved organic carbon EC – electrical conductivity TK – total potassium TKN – total Kjeldahl nitrogen VS – volatile solids TS – total solids COD – chemical oxygen demand

Jereb, G. Biodegradable municipal solid waste management. 1 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 1 INTRODUCTION Waste quantities are generally growing in all countries all around the world. Every year billions of tons of waste are generated. These wastes are result of activities in our homes, businesses and industries and disposal of all this large amount is an enormous environmental problem with many dimensions. Municipal, industrial and agricultural solid waste and biomass deposits cause large scale pollution of land and water. The generation of waste causes a loss of materials and energy and increase environmental costs on society for its collection, treatment and disposal. The impacts of landfill and incineration are significant because of their potential for greenhouse gas emissions (methane, carbon dioxide) and transboundary migration of organic micro-pollutants (dioxins and furans) and volatile heavy metals. Problems with waste are as old as human race. Very soon humans realized that waste are a potentional source of diseases and infections, so they dump their waste, which were totally biological, away from their settlements. The first organized municipal dump is in 500 BC outside ancient Athens in Greece, where regulations required waste to be dumped at least a mile from the city limits and covered with soil (Vuk, 1995). Until industrialization of society waste was mostly organic, so they can decompose naturally. Later, mostly because of industrialization, urbanization, and developing of consumer society amount of waste increase very fast. In Europe quantities of waste increasing in most western Europe (WE) countries and to a lesser extent in most countries in central and eastern Europe (CEE) and Twelve countries of eastern Europe, Caucasus and central Asia (EECCA). Landfilling remains the dominant waste disposal method in Europe. There are more than 3.000 million tones of waste generated in Europe every year. This equals 3,8 tones per capita in western Europe, 4,4 tones per capita in CEE and 6,3 tones per capita in EECCA. The collection of municipal waste varies considerably among countries, from 685 kg/capita (Iceland) to 105 kg/capita (Uzbekistan), what is seen in figure 1.1 (Okolje Evrope: Tretja presoja, Zbirno poročilo 2003).

Jereb, G. Biodegradable municipal solid waste management. 2 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004

Figure 1.1: Municipal waste collected in selected countries in WE, CEE and EECCA (Okolje Evrope: Tretja presoja, Zbirno poročilo 2003: 42)

In year 2001 in Slovenia we collected around 550.000 metric ton of domestic waste (282 kg per citizen) and another 290.000 metric ton of municipal waste from industry, trade and other activities (149 kg per citizen). Together all municipal solid waste, collected in Slovenia, represent amount of 840.000 metric ton per year (439 kg per citizen) (Agencija RS za okolje, 2003). The treatment and disposal of wastes, which are mainly of organic origin, is one of the most important problem and greatest challenge facing mankind. Environmental degradation is often caused by mismanagement of wastes. Human health relies on environmental health, which can be measured as air, water and food quality. People have become more environmentally conscious and any kind of system that could contribute to health problems becomes a public issue. Most of cultivation systems, such us forestry, agriculture, horticulture, aquaculture, and green urban areas, use petroleum-based, chemically synthesized fertilizers, pesticides and other chemical substances. All these systems also use energy transformed mainly from fossil energy carriers. On the other hand, there is a great amount of plant nutrients and bioenergy in organic waste, residues, by-products and fuel crops. These renewable raw materials can be efficiently upgraded in bioconversion systems, plant nutrients can be recycled and bioenergy can be used (Gajdoš, 1998).

Jereb, G. Biodegradable municipal solid waste management. 3 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 Biological treatment of solid, liquid and gaseous wastes is probably the only way that leads to sustainability. All biodegradable wastes can be treated by product-oriented processes of bioconversion in facilities using advanced technology. Regulating and speeding up natural biological processes, for example short-time composting, can be one of the steps to achieve an optimal system for processing organic waste. The products like compost or biofertilisers of desired quality can be used as growing medium or horticultural substrate, substitute for peat in a container medium for the nursery plants, soil improvements that influence the physical, chemical and biological properties of the soil (Gajdoš, 1998). The common treatment processes for biological waste are composting, anaerobic decomposition (also called anaerobic digestion) and fermentation. Biological treatment of solid waste includes processes that rely on microbes to change or degrade organic waste in a controlled manner. Microbes are very sensitive to changes in environmental conditions. Mayor factors affecting microbial activity are moisture, temperature, pH, oxygen concentration, presence of toxic elements or compounds and type and quality of organic material as food supply for microbes. During decomposition of organic material different gases are produced. Gaseous products of waste decomposition pollute the air and contribute to global warming. Uncontrolled release of the gaseous product of waste decomposition into the atmosphere contributes to global warming. Decomposition of each metric ton of solid waste could potentially release 50 – 110 m3 of carbon dioxide (CO2) and 90 – 140 m3 of methane into the atmosphere (Vieitez et al., 1999).

Jereb, G. Biodegradable municipal solid waste management. 4 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 2 EUROPEAN COUNCIL DIRECTIVE ON THE LANDFILL OF WASTE The European Council Landfill Directive (1999) will have a profound effect on collection and processing of biodegradable waste in member states. Composting will have an important role in processing much of the biodegradable waste, which in future will have to be diverted from landfill. Directive regulates which waste and treatment are not acceptable in landfills. All member states shall set up a national strategy for the implementation of the reduction of biodegradable waste going to landfills. This strategy should include measures to achieve the targets of recycling, composting, biogas production or materials/energy recovery. This strategy shall ensure that not later than in five years biodegradable municipal waste going to landfills will be reduced to 75 % of the total amount (by weight) of biodegradable municipal waste produced in 1995 or the latest year before 1995 for which standardized Eurostat data is available. After eight years reduction must be up to 50 %, and not later than after 15 years the reduction must be up to 35 %.

Jereb, G. Biodegradable municipal solid waste management. 5 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 3 COMPOST POTENTIAL OF ORGANIC FRACTION OF SOLID WASTE Organic fraction of municipal solid waste (OFMSW) has been identified as a heterogeneous material in which the composition varies widely. The composition is depend by regional differences, climate, extent of recycling, collection frequency, season, cultural practice, as well as changes in technology. It depends also by various method of collecting and sorting system (mechanically sorted, source sorted or hand sorted organic fraction of waste) (Gunaseelan, 1997). On the School of agricultural technology on technological and educational institute of Crete Manios (2004) has research different organic solid waste compost potential and development activities, related to the production and evaluation of compost derived from a variety of local solid, mainly agricultural organic wastes. Materials, such as olive press cake, olive tree leaves and branches, vine branches, pressed grape skins, pig manure, sewage sludge and the organic fraction of municipal solid waste (OFMSW) have been evaluated for their behavior during composting, their compatibility in mixtures and the quality of the end product. The preparation of raw feedstock materials included shredding (where necessary), addition of inorganic N to correct the C/N ratio to an optimum value of 30:1 and mixing of the different feedstock materials. All material was composted mainly by using windrows. The quality evaluation included a detailed physiochemical (pH, electrical conductivity, nutrients concentration, heavy metal concentration, etc.) and biological analyses (pathogenic microorganisms), and also an agronomic evaluation, in which composts were used as a soil amendment for cultivation of local vegetables. All organic wastes tested can be composted in a satisfactory manner. However, mixtures should be used to ensure a good final product. Also mixing different fractions of organic waste include easy handling of the materials during composting and reduced odour emissions, as well as fewer turnings, less need for C/N ratio correction and moisture adding, and a shorter thermophilic and maturation phase. Shredded olive tree leaves, olive tree branches and vine branches are effective bulking agents for mixing and composting with pressed grape skins, pig manure, sewage sludge, OFMSW and vegetable waste (moisture content > 55%) in a number of ratios and combinations. The optimum ratio of drier and wet waste is 2:1 by volume to produce windrows that can be easily shaped and turned with minimum leaching and odours. An average number of five to six turnings during the thermophilic phase were adequate when combined with water addition where necessary. The duration of the thermophilic phase varied according to the materials and the number of turnings. The physico chemical characteristics of the mature composts were correlated with the properties of the raw feedstock rather than the process itself. These results suggested that composts can partially replace peat from substrate mixtures in a number of uses. Compost can also be used as a soil amendment in open air and green house cultivation, with a suggested rate of application of 100–130 m3/ha (equivalent to 50 – 70 t/ha) in the first year (Manios, 2004).

Jereb, G. Biodegradable municipal solid waste management. 6 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 4 BIOLOGICALLY BASED METHODS FOR MANAGEING ORGANIC

WASTE Processes employed to compost source segregated household waste vary considerably throughout Europe. The simplest and by far the most common are outdoor windrow systems. These typically comprise long rows of waste (windrows) which are mechanically turned by a vehicle to aerate and mix the waste, thus promoting rapid decomposition. These simple outdoor systems are mainly used to compost garden waste. Enclosed composting operations tend to be more sophisticated and often use computer controlled, fully automated tunnel, channel and box processes. These more technically advanced processes often employ forced aeration systems and environmental protection measures to control odour emissions. They are typically used to process the more putrescible fractions of MSW, such as kitchen waste (Slater and Frederickson, 2001). 4.1 CODIGESTION OF MUNICIPAL SOLID WASTE AND BIOSOLIDS The feasibility and benefits of the anaerobic co-digestion of sewage sludge and organic fraction of municipal solid waste are dilution of potential toxic compounds, improved balance of nutrients, synergistic effects of microorganisms, increased load of biodegradable organic matter and better biogas yield. Additional advantages include hygienic stabilization, increased digestion rate, etc., when the process occurs under thermophilic conditions. Sosnowski et al. (2003) was hold the experiments in two different systems, first in a 40 dm3 bioreactor operated thermophilically in batch mode and second in quasi-continuous mode in two separated stages: acidogenic digestion in the continuous stirred tank bioreactor of volume 9 dm3 under thermophilic conditions (56 °C) and mesopholic methane fermentation (36 °C) in the bioreactor of volume 14 dm3. Five series of experiments were hold. In first two, sewage sludge and OFMSW was hold in batch bioreactors; in 3rd OFMSW, in 4th sewage sludge and in 5th mixture of sewage sludge and OFMSW was used in a quasi-continuous mode in two stage reactor. During experiments they found that the cumulative biogas production of the mixtures of sewage sludge and the organic fraction of municipal solid waste increased with increasing proportions of the municipal solid waste, but the biogas production was achieved more slowly at higher than at lower organic load. The two-stage experiments conducted in quasi-continuous mode were generally more effective, therefore the separation of acidogenic and methanogenic stages is reasonable; in particular conducting one of the stages under thermophilic conditions is advisable taking into account the hygienic stabilization of the final product. The anaerobic co-digestion of sewage sludge and organic fraction of municipal solid waste seems to be an attractive method for environmental protection and energy savings. Stroot et al. (2000) evaluate the feasibility of codigestion of the OFMSW, primary sludge, and waste activated sludge in mesophilic (37 ºC), laboratory-scale digesters. The feed for experiment was mixture of simulated OFMSW, primary sludge and waste activated sludge. For the laboratory scale anaerobic digester they use a 2 litres Pyrex bottles with working volume of 1 litre (experiment 1 and 2) and 500 ml (experiment 3). Digesters were operated at mesophilic conditions (37 ºC). Digesters were continuously mixed (CM) on a shaker table or minimally mixed (MM) by hand for two minute per day. pH was controlled (if pH < 7) by adding NaOH, NaHCO3 or KHCO3 or by reducing daily feed rate. Biogas was collected in Tedlar bags and was measured daily using liquid displacement. Total volatile fatty acids concentration, alkalinity, Ph, and biogas production was measured daily. Biogas composition,

Jereb, G. Biodegradable municipal solid waste management. 7 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 individual volatile fatty acids concentration, solids and fiber content were measured 2 – 3 times per week. In first experiment different startup strategies were compared using four digesters operate under continuosly mixed conditions. They found that anaerobic active sewage sludge serves as excellent inoculum to accomplish fast startup of codigestion treating of organic fraction of municipal solid waste and sewage sludge. During second experiment six digesters were operated to compare performance under continuous mixing and reduced mixing levels at various loading rates and solids levels. The continuously mixed digesters exhibited unstable performance at the higher loading rates, while the minimally mixed digesters performed well for all loading rates evaluated. Also the nonmixed digester exhibited a higher methane yield than the continuously mixed digester. In third experiment authors proved, that unstable, continuously mixed digester was quickly stabilized by reducing the mixing level. With these experiments authors confirmed that continuous mixing was not necessary for good performance and was inhibitory at higher loading rates. So reduction of mixing levels may be used as an operational tool to stabilize unstable digesters (Stroot et al., 2001). 4.2 pH AND TEMPERATURE REGULATION CONTROL METHOD An initial phase characterized by a low pH is often observed during composting of organic wastes and perhaps especially of easily degraded energy-rich materials like household waste. The pH in household waste often already has a low pH when it arrives at the composting plant. Smars et al. (2002) found that a considerable gain in time and process activity can be obtained by a mesophilic control of the temperature during the initial low pH phase of the compost process. Experiment was conducted from 1998 to 2001. For feed in reactor they use source separated organic household waste and chopped wheat straw. The proportion of household waste, straw and water were adjusted to give a initial water content of 65 % w/w and C7N ratio 22. The compost material were homogenised and put in 200 litres airtight reactor. The reactor layout is present in figure 4.1.

Jereb, G. Biodegradable municipal solid waste management. 8 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004

Figure 4.1: A simplified description of the compost reactor, indicating where CO2, O2, temperature and pH in compost material and condensed liquid were measured (Smars et al., 2002: 238)

The reactor was thermally insulated and equipped with a fan to mix the compost gases in order to eliminate gradients in temperature and gas composition. It was also equipped for independent control of oxygen level and temperature in the compost matrix. The system was equipped for continuous monitoring of gas flow and emission of CO2 and other gases from the reactor. The water content in the compost matrix was controlled by adding water to compensate for moisture losses due to drying as an effect of heat production and aeration. The evaporated water was trapped as condensate in a cooler which serves as part of the regulation system. The condenser also enables measurements of pH in the condensate. In reactor material was daily mixing to even out moisture gradients, exposing new surfaces and keeping the material permeable to airflow. During experiment Smars et al. (2002) test whether the composting process during the initial low pH phase in household waste composting under good oxygen conditions could be shortened by keeping temperature below 40 ºC until pH indicated absence of acids. Experiment was hold by two different regimes, the first regime (Regime I) involved self-heating by the biomass to naturally raise the temperature to 55 ºC, followed by regulation of the temperature at a constant 55 ºC. The second regime (Regime II) involved natural self-heating by the biomass to the temperature of 35 ºC, followed by regulation of the temperature at 37 ºC until the pH in the condensate rise to pH 5. When the pH exceeded 5, the temperature regulation was turned off until the temperature had reached 55 ºC. The temperature was then kept constant at 55 ºC. The experiments were run until at least 45% of the initial carbon content was converted into CO2. They found that regime I experiments and regime II experiments were similar within treatments, a trend is illustrated in figure 4.1, which shows the cumulative CO2 turnover of each experiment. It also shows that the gain in time occurs early and seems to be maintained.

Jereb, G. Biodegradable municipal solid waste management. 9 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004

Figure 4.2: The cumulative CO2–C emissions of the 3 + 3 Regime I and II runs (Smars et al., 2002: 240)

Table 4.1 presents the time taken to achieve 10%, 20%, 30%, 40% and 45% of cumulative CO2–C emissions for the two regimes. As seen from Table 1, the mean time until 10% carbon turnover was reduced from 4.4 days in regime I to 1.8 days in regime II. Table 4.1: Time taken to reach different levels (10%, 20%, 30%, 40%, 45% of initial C) of cumulative CO2–C emissions in days (Smars et al., 2002: 240)

Regime % of CO2–C emission

10% 20% 30% 40% 45%

I

1 3,78 5,35 7,20 8,34 9,23 2 5,04 6,00 7,09 8,26 9,00 3 4,43 5,29 6,30 7,35 8,06

Mean 4,41 5,55 6,86 7,98 8,76 II

1 1,96 2,62 3,56 4,50 5,20 2 2,03 2,81 3,95 5,17 5,81 3 1,37 2,23 3,01 4,14 4,78

mean 1,79 2,55 3,51 4,60 5,27 The results of that experiment shows that a considerable gain in time and process activity can be obtained by a mesophilic control of temperature during initial low pH phase of the composting process.

Jereb, G. Biodegradable municipal solid waste management. 10 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 4.3 DECOMPOSITION OF FOOD WASTE Various methods used for the treatment of food wastes, include landfilling, incineration, composting, feed for animal and complete decomposition. The landfill method cause secondary environmental problems such as pollution of ground and/or surface water and offensive odours. Food wastes containing high salt concentration, that why is not suitable feedstock for composting. Lack of nutrients as well as sanitary problems restrict recycling of food wastes as animal feed. Ik Park et al. (2002) introduce a slurry bioreactor system for high-rate decomposition of food waste. It was found to be highly effective, based on both decomposition rate and extent. In the study of long-term operation of a pilot scale slurry bioreactor was conducted to evaluate the practical applicability of a slurry-phase food waste decomposition system. 80 litres stirred tank reactor (50 litres working volume) was used as a slurry bioreactor. The reactor was equipped with a pitched blade turbine-type impeller and sparger for agitation and aeration. The previously prepared microbial mixture (500 ml) was placed in the bioreactor, and the working volume was adjusted to 50 litres by adding tap water. The reactor operates at room temperature (20 +/- 5ºC), with agitation speed of 120 rpm and aeration rate of 50 litres per minute. The concentration of dissolved oxygen and pH were measured by submerging electrodes. Tap water was supplemented to the reactor at every sampling time to compensate for loss of water due to evaporation and to keep the working volume constant. They also measured dissolved organic carbon and elemental composition of suspended solids. During operation, approximately 750 g of wet food waste was added daily to the reactor without intermittent removal of process residues such as not-easy or non-biodegradable matter to simulate operation of a full-scale system. Food wastes were collected from a Korean food restaurant on the campus of Pohang University in Korea. During the treatment of 13.2 kg dry weight (67.5 kg wet weight) of food waste over a period of 90 days, 1.2 kg dry weight of suspended solid remained in the bioreactor, corresponding to 91% reduction of solid waste. This pattern of operation would be practical for restaurants where food wastes are collected and discharged on a daily basis. Furthermore, the oxygen requirement was estimated from long-term operating results to use for design and scale-up of slurry bioreactor systems (Ik Park et al., 2002). 4.4 VERMICOMPOSTING MUNICIPAL SOLID WASTE WITH EARTHWORMS Kaviraj and Sharma (2003) made a comparative study, which has take place in India, between exotic and local species of earthworms for the evaluation of their efficiency in vermicomposting of municipal solid waste. They select two different species of worms, one is domestic species L. mauritii, collected from soil in Indian institute of technology in New Delhi, the other species E. fetida were obtained from an earthworm bank. Municipal solid waste is highly organic, that's why vermicomposting has become an appropriate alternative for the safe, hygienic and cost effective disposal of organic waste. Earthworms feed on the organic matter and convert it into casting (ejected matter), rich in plant nutrients.

Jereb, G. Biodegradable municipal solid waste management. 11 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 The action of earthworms in the process of vermicomposting of waste is physical and biochemical. The physical process includes substrate aeration, mixing as well as actual grinding, while the biochemical process is influenced by microbial decomposition of substrate in the intestine of earthworms. Vermicomposting of organic waste accelerates organic matter stabilization and gives chelating and phytohormonal elements which have a high content of microbial matter and stabilized humid substances. For experiment Kaviraj and Sharma (2003) use organic waste from local waste collection site, where organic waste was separated manually. The waste was pre-decomposed for 8 days prior to study. The experiments were conducted in earthen pots, each of capacity 2 kg of waste, with a small hole at the bottom. A total of 54 earthen pots were used and kept in three sets of 18 pots for E. fetida, L. mauritii and control (without any earthworms). In each pot was taken one kilogram of waste along with 100 g of cowdung and 100 g of soil for providing an initial environmental condition for the worms. In each of two sets of earthen pots twenty healthy earthworms of the same size (E. fetida and L. mauritii) were introduced. Moisture content was maintained between 40% and 60% during the study. The duration of experiments was six weeks. During experiment they chemically analyse raw organic waste and vermicompost samples, collected weekly, for total organic carbon (TOC), total Kjeldahl nitrogen (TKN), total potassium (TK), electrical conductivity (EC) and pH. In study authors found, that on the basis of chemical analysis, species E. fetida is superior in performance over L. mauritii, in terms of loss of total organic carbon (TOC), reduction in carbon to nitrogen ratio, increase in electrical conductivity (EC) and total potassium (TK). Although the epigeic species of earthworms (i.e. E. fetida) are capable of working hard to convert all the organic waste into manure, they have no significant value in modifying the structure of soil. The anaecic (like L. mauritii) however, are capable of both organic waste consumption as well as modifying the soil structure (Kaviraj and Sharma, 2003).

Jereb, G. Biodegradable municipal solid waste management. 12 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 5 BIOGAS AND COMPOST Most organic waste can be used as renewable raw materials suitable for bioconversion. The units for local handling of solid and liquid organic waste from households will work to the principle of closed loop. All urban organic waste, such as garden waste, food residues, paper, human excreta from households, restaurants, commerce, small industries, can be treated in bioconversion systems and can be transformed into energy-rich biogas and valuable, reproducible biofertilisers (Gajdoš, 1998). The anaerobic digestion of organic solid waste produces biogas, so innovative systems of combined methods of anaerobic digestion and aerobic composting are proposed for the recovery of energy and the production of compost from organic fractions of household wastes (Krzystek et al., 2001). 5.1 PRODUCTION OF BIOGAS AND COMPOST BY MIXING

AEROBIC/ANAEROBIC CONDITIONS Krzystek et al. (2001) investigate the sequence of biological aerobic and anaerobic digestion of organic solid waste. For organic reactor feed they use OFMSW from city of Lodz, collected fresh and grind in laboratory to a size 1 – 3 mm. So grind waste diluted with tap water was put in to bioreactor. The experimental data cover series of batch and continuous aerobic biodegradation processes as well as series of batch anaerobic digestion processes in laboratory scale reactors. During biodegradation processes they analysed total solids (TS), volatile solids (VS), COD, most probable number of microorganisms, activity of microorganisms, TOC, DOC, TKN, volume of biogas production and methane fraction of biogas. Aerobic processes were carried out in the stirred tank reactor and air-lift reactor of working volume 6 and 18 dm3. The bioreactors were equipped with standard control instrumentation: temperature, pH, dissolved oxygen level, foam level and stirrer speed. Anaerobic processes were conducted batch wise at the temperature of 36 ± 0.5 °C and pH > 6 in the stirred tank reactor of 10 dm3 of total volume. A cycle of aerobic and anaerobic processes was carried out in various sequences (aerobic – anaerobic and anaerobic – aerobic). The amount of biogas obtained in the anaerobic process not preceded by the aerobic process was almost four times higher than in the reverse sequence. The changes in biogas volume obtained in alternative sequences of aerobic / anaerobic processes are illustrated in Fig. 5.1. However, the total degree of reduction of the main indices of organic load (volatile solids (VS), chemical oxygen demand (COD) and dissolved organic carbon (DOC)) of the two sequences was similar.

Jereb, G. Biodegradable municipal solid waste management. 13 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004

Figure 5.1: Biogas volume in alternative sequences of batch aerobic and anaerobic processes (Krzystek et al., 2001: 109)

5.2 METHANE PRODUCTION One-third of the energy that can be recovered by incineration of domestic waste can be recovered as methane gas. In combined bioconversion processes the energy, which is transformed by microorganisms to energy-rich methane, can be transformed to electricity and heat, only heat, or to fuel for use in engines. And there will still be a great amount of energy bound in biofertilisers, which are the solid remainder of bioconversion of organic waste. Biofertilisers contain plant nutrients and bioenergy in the not completely decomposed organic material, in newly built humid substances, and in the microbial biomass (Gajdoš, 1998). During methane fermentation the two main processes occur:

– acidogenic digestion with the production of volatile fatty acid; and – the volatile fatty acids are converted into CH4 and CO2 (Sosnowski et al., 2003).

The fruit and vegetable solid waste form the bulk of wastes originated from domestic kitchen. They are dumped into municipal landfill and significantly contribute to the OFMSW. Gunaseelan (2003) investigate the biochemical methane potential of fruit and vegetable solid waste. He found that substantial differences were observed in the methane yields and kinetics among the varieties of fruit and vegetable solid waste, but most of them have methane yields greater than 0,3 litre g–1 VS added and thus represent an excellent choice for commercial methane production. All tested samples of fruit and vegetable solid waste gave monophasic

Jereb, G. Biodegradable municipal solid waste management. 14 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 curves of methane production and more than 90% of the methane yield was achieved between 40 and 50 days of fermentation. Biomass is defined as contemporary plant matter formed by photosynthetic capture of solar energy and stored as chemical energy. That energy from biomass can be converted in anaerobic digester for production of methane. Almost all the land and water based species, so all biomass have good digestion characteristic or can be pre treated to promote digestion, so it is a potentional source for methane production. The anaerobic digestion potential of organic fraction of municipal solid waste as also all others biosolids based on the volatile solids content and the percentage of poorly biodegradable materials, such as paper, wood etc. The methane yield from organic fraction of municipal solid waste can be classified into three groups. Methane yield from hand sorted OFMSW with a range of 0,39 - 0,43 m3kg-1 VS added, mechanical sorted OFMSW with a range of 0,18 - 0,26 m3kg-1 VS added and pre–composted OFMSW with less then 0,14 m3kg-1 VS added. The anaerobic digestion potential of OFMSW increases in systems with co–digestion with sewage sludge (Gunaseelan, 1997). 5.3 HYDROGEN PRODUCTION FROM ORGANIC WASTE Interest in hydrogen as a renewable fuel was rekindled in the 1990s when it became clear that carbon dioxide production from combustion of fossil fuels may cause significant global climate changes. One possible approach to producing hydrogen is to use dark fermentative hydrogen from low-cost substrates like organic wastes. Nielsen et al. (2001) combined waste remediation and biological hydrogen production in a process where a large proportion of the hydrogen produced can be collected, free of other gaseous species from the fermentation. Hydrogen is a key intermediate in the overall anaerobic oxidation–reduction reactions involved in the mineralisation of organic matter, and the concentration of hydrogen plays a central role in controlling the proportions of the various products generated during the fermentation. Many hydrogen-producing reactions are thermodynamically unfavourable unless the partial pressure of hydrogen is kept low. In natural ecosystems, this is achieved with syntrophic associations between hydrogen-producing (acetogenic) and hydrogen-consuming (methanogenic) bacteria. With artificially removal of hydrogen, the partial pressure of hydrogen can be kept low in the absence of hydrogen-consuming methanogenic bacteria. But hydrogen is not the only gaseous species produced, so pure hydrogen as a fuel has to be extracted from other gases (mainly CO2) produced during fermentation. So gas stream from the bioreactor passes through a sulphide trap (used to prevent contamination of the membrane by sulphur-containing gases (e.g. hydrogen sulphide)) and then through a heated palladium–silver membrane to separate hydrogen from the gas stream. Palladium-based membranes possess catalytic activity and have a high selectivity towards hydrogen. Hydrogen can adsorb to the upstream membrane surface and dissociate (Nielsen et al., 2001).

Jereb, G. Biodegradable municipal solid waste management. 15 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 In experiment, hold by Nielsen et al. (2001), authors represent a hydrogen production from organic waste. For feed in bioreactor they use a mixed anaerobic culture that originated from four different sources: thermophilic household compost (500 g), waste from a landfill simulation reactor (methanogenic stage; 100 g), landfilled municipal solid waste from Filborna landfill (Helsingborg, Sweden, 200 g), and garden soil (200 g). The waste fractions were added to a 5 L glass bottle flushing with nitrogen gas followed by the addition of 2 L of tap water. Reactor was then closed with a silicon stopper, equipped with gas drainage tubing and incubated at 37 ºC. The bioreactor was constructed with a 4-litre glass vessel that was continuously sparged with nitrogen (30 ml/min) introduced from the bottom in order to displace gas from the simulated household waste. During the filling of the reactor, waste and inocula (in total 500 ml) was put in layers during continuous flushing with nitrogen in order to maintain anoxic conditions. After inoculation, the bioreactor was placed in a water bath at a temperature of 37 ºC. The output gas volume from the reactor was measured with gas meter based on the principle of water displacement. Schematic diagram of experiment is shown in figure 5.2, where 1 is sampling point between the bioreactor and the sulphide trap, 2 and 3 are sampling points before and after the membrane reactor.

Figure 5.2: Schematic diagram of experimental aparatures, (Nielsen et al., 2001: 548)

The sulphide trap consisting of beds of zinc oxide held at 250ºC was introduced to remove hydrogen sulphide and probably also other sulphur-containing species from the gas stream leaving the bioreactor. The palladium–silver membrane is consisted of a cylinder palladium–silver alloy coated with a thin layer of pure palladium. The gas from the reactor passed through the inside of the membrane and the hydrogen permeated from the inside to outside. The outside of the membrane was held under a vacuum. The membrane unit was placed in an insulated cavity and the operating temperature was about 350 ºC.

Jereb, G. Biodegradable municipal solid waste management. 16 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004

Figure 5.3: Hydrogen concentration as a function of time during the fermentation in the bioreactor (□), and both before (∆) and after (*) the Pd/Ag membrane (Nielsen et al., 2001: 549)

Authors demonstrated, that hydrogen can be extracted from the fermentation products of household waste by the use of palladium – silver membrane. As shown in fig. 5.3, between 85 and 90% of the hydrogen was removed by the membrane throughout the study. It was also observed that the sulphide trap (ZnO) did not remove significant amounts of hydrogen. 5.4 COMPOST USAGE It looks like that increasing legislation and higher environmental standards have been responsible for encouraging the development of a new generation of composting facilities throughout Europe. A cornerstone of the new approach to composting has been the realization that only good quality compost derived from uncontaminated wastes has the potential to be sold to the public, used in agriculture or in large-scale reclamation projects (Slater and Frederickson, 2001). For agriculture, organic waste materials represent an inexpensive nutrient source and soil conditioner. Recycling of sewage sludge is already common practice, the recycling of sewage sludge was 30% in Canada and 40% in the UK (Petersen et al., 2003). In Western Europe, current trends in waste management policies favor land application as opposed to land fill deposition or incineration (European Council Directive, 1999). Petersen et al. (2003) studied different organic fertilizers, such us sewage sludge, household compost and solid pig manure. They put them under field and greenhouse conditions to describe their fertilizer value and effects on soil properties and soil biota, the fate of selected organic contaminants, and their potential for plant uptake. A 3-year field trial on two soil types showed that there are no adverse effects of waste amendment on crop growth and also a significant fertilizer value of one sludge type. They didn’t found any adverse effects of organic waste application on soil or crop and for some waste products a positive effects were observed.

Jereb, G. Biodegradable municipal solid waste management. 17 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 The organic waste generally showed no adverse effects on crop yields, soil fertility or biological activity, but rather a stimulation of some properties. The levels of typical organic contaminants decreased considerably within a period of 6–12 months after the time of application, and the monitoring carried out at the end of the 3-year field trial gave no indications of long-term accumulation. Also, there was no evidence for plant uptake of the organic contaminants studied (Petersen et al., 2003). 5.5 SOURCES OF HEAVY METALS IN BIOWASTE COMPOST Separately collected organic fraction of municipal solid waste can be reused for soil conditioning after composting. In this way landfilling or incineration can be reduced. But frequent application of composts to soil systems may lead to the accumulation of heavy metals in soils. The heavy metals content in biowaste-composts frequently exceeds the legal standards. With that conflict between two governmental policies appear: the recycling of solid waste on the one hand, and the protection of natural ecosystems and public health on the other hand. Veeken and Hamelers (2002) were compared the heavy metal content (Cd, Cu, Pb and Zn) of biowaste with the natural background content of Cd, Cu, Pb and Zn in the different constituents of biowaste. They are tried to establish whether biowaste is contaminated with heavy metals from other unknown sources. They found that a large amount of biowaste was not organic, but over 50% was made up of soil minerals due to the collection of biowaste constituents from gardens. The heavy metal content of the various fractions in biowaste was compared with the natural background contents of heavy metals in the constituents of biowaste, i.e. food products, plant material, soil organic matter and soil minerals, by collecting literature data. They found, that heavy metal content in the fractionated physical entities of biowaste corresponds with the natural background concentration of heavy metals of the biowaste constituents. This shows that biowaste is not contaminated by other unknown sources. A large amount of biowaste is not organic, but is made up of soil minerals; this is because approximately 80% of biowaste is collected outdoors, i.e. in gardens and mainly consists leaves, grass and branches, but also of garden topsoil, which introduces a substantial amount of soil components into the biowaste. The indoor fraction is composed of organic matter collected in the kitchen (e.g. food remains and coffee filters) and indoor plant material, such as flowers and houseplants. The heavy metal content in the fractionated physical entities of biowaste corresponded with the natural background concentration of its constituents and indicated that biowaste was not contaminated by other sources. However, the natural background content of biowaste constituents will result in heavy metal contents for biowaste compost that will exceed the legal standards. That’s why authors recommended that the legal standards for composts should be critically re-examined. The protection of soil systems could be better guaranteed if the input of heavy metals was evaluated for all inputs of fertilisers and soil conditioners, i.e. animal manures, various types of compost and artificial fertilisers (Veeken and Hamelers, 2002).

Jereb, G. Biodegradable municipal solid waste management. 18 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 5.6 COMPOST USING AS A LANDFILL CLOSURE CAPS Landfill final closure cap must be covered with a cover that minimizes the long-term migration of liquids through the landfill. The main objective of covering systems is to reduce or eliminate the transport of fluids through the waste. Covering systems must function with minimum maintenance, promote drainage, minimize erosion of the cover, accommodate settling, and have hydraulic conductivity less than or equal to that of any bottom liner system or natural soil present (Elshorbagy and Mohamed, 2000). Covering systems of landfills involve partial or complete isolation of waste materials from the surrounding environment. Elshorbagy and Mohamed (2000) investigate the performance of a native soil available in arid areas blended with municipal solid waste compost as an infiltration barrier layer in landfill closure cap design. During the experiment they measured specific gravity, moisture – density relations of soil and soil aggregated mixtures, ph and electrical conductivity of soil around landfill and compost from Dubai composting factory. The native soil present at the landfill sites is mostly sandy soil with optimum moisture content of 12% (by wet weight) corresponds to dry unit weight of 1800 kg/m3. Clay and other cohesive materials are very rare in the region. That’s why authors of the study decided to explore the possibility of blending the native soil with the produced municipal solid waste compost and evaluate the performance of different blends as hydraulic barriers in final closure caps for the existing landfills. The developed mixture of 60% compost and 40% native soil was found to have a hydraulic conductivity 4,0 to 6,0 x 10-9 m/s. From the hydraulic performance viewpoint, it is concluded that the developed mixture is an alternative. The presented study has shown that the municipal solid waste compost can be used in construction of hydraulic barrier layer in landfill closure caps in arid areas. The cost benefits of such usage can be potentially doubled if the compost, required for the mixture, was manufactured at the site (Elshorbagy and Mohamed, 2000).

Jereb, G. Biodegradable municipal solid waste management. 19 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 6 CONCLUSIONS Waste is material, which have little or no value to producer or consumer. Humans with nearly all activities produce waste. Waste quantities growing all over the world every year. So every day we produce more and more waste, which we have somehow treated. Very common practise till now was collecting all waste together and put in landfill or even incinerate them, and all that cause large scale pollution of land and underground water and soil. Changes in nature of wastes, concern for environment and desire to recover resources from waste stream have stimulated the development of new waste management technologies and processes. The major component of municipal solid waste represent organic fraction, mostly from our homes, kitchen waste like food, paper and cardboard, garden waste like tree leaves and branches, grass, rotten fruit and vegetable, etc. And all this loads of waste end up on municipal landfill. But most of them are filled up or will be in next few years. By decomposition of organic waste a biogas spring up in such landfill. Beside CO2 a large amount of CH4 originate and emit in air, and both are wormhouse gases. To avoid emission in the air and water, new trends in municipal waste management have been adopted. European Council Landfill Directive (1999) was adopted to solve collection and processing of biodegradable waste in member states. Composting will have an important role in processing much of the biodegradable waste, which in future will have to be diverted from landfill. There are many different methodts to deling with organic fraction of municiple solid waste. Each method has its own solutions and problematic. Organic fraction of municipal solid waste is a complex highly variable waste stream. To achieve quality compost, organic waste must be appropriate processed. This processing includes shredding or grinding to reduce size and at same time to removal plastic, metal and other nonbiological material. After pre-treatment the composting stage is followed. Term composting is usually used for biological treatment processes - either aerobic or anaerobic. A very old classic way of composting is windrow or heap composting, where biological waste are simply put in a heap or windrow and aerate with turning. But in that kind of biological waste composting no biogas can be capture, a large area are require, and also process is relatively slow. Because of all that and also lack of appropriate place for landfills, all existent landfills are getting full, our land (soil), water, particulary undergrownd water and air prevention, resource recovery and so on, today in all developed countries are developing new methodts for manageing with organic fraction of municipal solid waste. Codigestion of municipal solid waste is based on codigestion different fractions of organic waste. Mixing fractions have some benefits, like dilution of potential toxic compounds, improved balance of nutrients, synergistic effects of microorganisms, increased load of biodegradable organic matter, better biogas yield, hygienic stabilization, increaseing digestion rate, etc. With mixing we can also regulate pH of organic material. In spite all advantages caution should be present by selection of different fractions of waste, because if one fraction is toxic, whole product - compost can be also toxic.

Jereb, G. Biodegradable municipal solid waste management. 20 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 With pH and temperature regulation during composting we can achive a considerable gain in time and process activity. This method is based on cintroling temperatures on different levels during different stages of process of composting. However, top temperature, that is achive, is 55 ºC and is not high enough to kill all potentional pathogen microorganisms and their spores, especially if for feed in such bioreactors mixed organic fraction of municipal waste is used. Vermicomposting of municipal solid waste with different species of earthworms is absolutely biological or should I say sustainable approach, if some domestic species of earthworm is chosen for active organism. In case, that we choose some foreign species, is question how will this new species react in new environment and also what will mean this new species for ecosystem, ergo what influence will it have. Production of biogas, methane or even hydrogen from organic fraction of municipal waste is absolutely important method of biological waste decomposition. We can organic waste with appropriate method transform into energy rich biogas and compost as biofertiliser. This biogas can be used for heat or electricity production (or even both), as well as storable fuel for full cell. But the question is, do we need all this sophisticated methods and expensive instruments and equipment (like palladium – silver membrane, sophisticated bioreactors and so on) with which we can “extract and catch biogas, but on the other hand enormous quantity of natural gas, by product of coalmining and oil pumping is burned on place or just released in the atmosphere. Compost is commonly used for fertiliser in agriculture, soil conditioner, for turn green the road embankment, also for landfill closure caps etc. there are already some studies, in which researcher research effects of using compost as fertilizer or soil conditioner. But I think that we should be very cautious with uptake compost from different origin and use it on fertile soil and environment. And I also think that more studies should be made in field of using compost and its potential influence on environment. It is good, that we devoted such high attention to different treatment technics for manageing waste, but I think, that more attention should be put on prevention of originate waste, reduce waste stream, reuse some materials before it is throw away and in the end recycle or proper disposal.

Jereb, G. Biodegradable municipal solid waste management. 21 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004 7 SUMMARY In all countries all around the world quantities of waste are generally growing. And all this waste is result of activities in our homes, businesses and industries. Disposal of all this large amount represent an enormous environmental problem with many dimensions. Municipal, industrial and agricultural solid waste and biomass deposits cause large scale pollution of land and water, generation of waste causes a loss of materials and energy. A large amount of municipal solid waste represent organic fraction of waste. All biodegradable wastes can be treated with processes of bioconversion in facilities using advanced technology. Regulating and speeding up natural biological processes can be one of the steps to achieve an optimal system for processing organic waste. European Council Landfill Directive (1999/31/EC) was adopted to solve collection and processing of biodegradable waste in member states. For processing organic fraction of waste a composting will have an important role. All kind of organic fraction of municipal solid waste are appropriate for composting. With mixing different fraction of organic waste even better results of composting can be achieved. For treatment of biological waste we can serve different techniques. Most common are composting, anaerobic decomposition and fermentation. In seminar is represent composting potential of OFMSW, some biologically based methods for managing OFMSW, also methods for biogas production and extraction, and some research of compost usage.

Jereb, G. Biodegradable municipal solid waste management. 22 Nova Gorica, Polytechnic Nova Gorica, Shool of Environmental sciences, 2004

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