for biogas and high value biofertilizer production · pdf filefor biogas and high value...

SWEET SORGHUM BIOGAS PLANT IN TEMPERATE REGIONS (BELGIUM) - DEMONSTRATION PLANT

FOR BIOGAS AND HIGH VALUE BIOFERTILIZER PRODUCTION

Andrea Salimbeni

European Biomass Industry Association

Rond-Point Schuman 6, 1040, Brussels, Belgium

ABSTRACT: Sweet sorghum is one of the most interesting energy crops. Due to its high photosynthetic efficiency

(3-4%) S.Sorghum hybrids have an impressive biomass yield per hectare at all latitudes ( up till 95 tons of fresh

biomass per ha per cycle). S. Sorghum is often cultivated in intensive plantations for the well known bioethanol

production. Anaerobic digestion is becoming a valuable alternative for s.sorghum processing due to the lower costs

and more “simple” installation. However, electricity and heat are still the main product obtained by biogas plant

where s.sorghum is processed. Objective of this study is to focus on high value biofertilizer production from sweet

sorghum energy crop, in order to evaluate the application of a new advanced anaerobic digestion technology to the

large sweet sorghum plantations as solution for biofertilizer production on site replacing artificial fertilizers demand,

thus reducing costs and GHG emissions. All of these aspects well be studied in a demonstration plant to be installed

in Belgium. The following paper can be easily divided in five main studies: 1-Evaluation of Sweet Sorghum Yield in

Temperate region; 2-New anaerobic digestion technology for fast sweet sorghum digestion; 3-First evaluation of

digester dimension and energy yield; 4-Biofertilizer production technology; 5-Preliminary economic evaluation.

Keywords: biofertilizer, sorghum, anaerobic digestion, biogas, digestate, pretreatment

1 SWEET SORGHUM IN TEMPERATE REGIONS

S. Sorghum hybrids are often cultivated in tropical

region for sugar and ethanol production. Intropical region

this plant provides two cycles per year and an impressive

biomass yield per hectare per cycle. However, the high

photosynthetic efficiency makes this biomass energy crop

a valuable solution for many bio-products as well as for

many European region. Trials made in Belgium showed a

biomass yield of about 70 tons of fresh biomass per

hectare, with a total grain production of about 5,4 tons

per ha. Of course only one cycle can be provided in this

cold weather country

1.1 Suitable Land

Sorghum is mainly grown on low potential, shallow

soils with high clay content, which usually are not

suitable for the production of maize. S.S. usually grows

poorly on sandy soils, except where a heavy textured sub-

soil is present. Optimal clay percentage in soil for sweet

sorghum plantation is 10 % - 30 %.

At the same time, this plant is more tolerant of

alkaline salts than other grain crops and can therefore be

successfully cultivated on soils with a pH (KCl) between

5.5 and 8.5. Source: FAO

1.2 Behaviour in low temperature conditions

Water does not represent a problem. Sweet Sorghum

requires about 4000 cubic meter of Water per ha.

Irrigation is required but rainy days in Belgium are

estimated to provide a valuable amount of water to be

stored. Source: FAO

The lower temperature for germination is 7 - 10 ºC.

However, the biomass yield in these condition is very

much lower than the real potential of this energy crop. In

order to have a suitable growing rate of Sweet Sorghum,

a temperature of 15 ºC is recommended to have a 80 % of

seed germinate. The best time to plant is when there is

sufficient water in the soil and the soil temperature is

15°C

Minimium sowing temperature is 14°C, so spring

time is recommended for firs sowing activity. However,

the optimum temperature for growing period are 22-

27°C. These high temperature required can represent a

problem in a cold region as Belgium is. However, many

trials demonstrated that a general temperature of 20 °C

can provide a valuable result in terms of biomass yield

and sugar content.

1.3 Belgium cultivation parameters

With relative high temperatures registrated only in

summer months like august and july, The plant yield

decreases of about 15%!.

Sweet Sorghum Intensive plantations provide about

93-95 tons/ha with ideal climate conditions. With a very

fast growing period of 120 days.

The estimated cultivating condition for sweet

sorghum hybrid in Belgium are defined as follows:

� Sowing: May

� Days requie before harvesting: 150

� Harvesting: September / October

Due to the low temperature in September /october,

the sugar content fermentation does not start immediately

and does not affect the storage. Thus, the harvesting

period can be extended of about 50 days, also using

specific different varieties.

Expected yield: 70 fresh tons per hectare.

Figure 1. Belgium average monthly temperature. Source:

Belgium climate forecast

21st European Biomass Conference and Exhibition, 3-7 June 2013, Copenhagen, Denmark

725

2 NEW CONCEPT S. SORGHUM PRETREATMENT

SYSTEM BEFORE ANAEROBIC DIGESTION

Even with low temperature, the main problem of

sweet sorghum silage usually produced for the biogas

production in many countries is represented by sugar

losses and time of retention:

Sugar Losses: 10% after two weeks storage

Mesophilic bacteria anaerobic digestion. RT: 115-130

days

The strategy for reducing the sugar losses and

increasing retention time is focused on a quenching

treatment of Sweet Sorghum sugar stalks. Immediately

after harvesting process. As first step, an overview on

Sweet Sorghum advanced harvesting logistic system is

shown below:

Harvesting Machine: CASE 7000 adopted and modified

for sorghum cultivation

Table I. Sweet Sorghum Harvester parameters. Source:

Case

Max high 4,5m

Max efficiency of stalks harvesting 1,5 t/min

Max harvesting speed 9 km/h

Fuel Capacity 480 l

Fuel consumption: ~ 80 l/ha

Average Harvesting speed 1 hour/ha

Estimated price 390.000

Mantenaince cost 2%

Sweet Sorghum harvesting machinery utilized will

allow to separate three different products. A tractor will

operate next to the harvester in order to collect all the

plant components. In addition, a Baler will be used to

collect leaves left on the ground.

• Grains & Panicles: Trailer 1

• Leaves: Ground. Bailing machine

• Stalks: 30 cm cut in trailer 2

A specific machinery will be used to separate grains

from panicles:

Grain Cleaner: Cicoria Atx 2000 C.

Table II. Grain cleaner parameters

Function: Separation of grains to panicles

Cost 39.000

Placement: Trailed by harvester or fixed in the

factory

Grains, separated from panicles, represent a valuable

source of income due to their (underestimated) 200 €/tons

market price as animal food.

Leaves will be collected by a Claas Baler

Table III. Leaves baler data

Capacity: 9 Bales/hour

Weight per bale 600 kg/bale

Speed 1,5 ha/hour

Cost 25.000

The total biomass harvested using this advanced

machinery is 70 fresh tons /ha, divided as follows:

Table IV. Sweet Sorghum plant main parts

Stalks 51,1 t/ha

Leaves 11,5 t/ha

Pannicles 2,31 t/ha

Grains 5,46 t/ha

Two main substates are recovered by Sweet Sorghum

fresh biomass:

1. Sugar juice

2. Solid biomass

Stalks are quenched with water to extract sugar juice

from fiber and separate bagasse from liquid part.

The raw Sugar Juice properties are listed below:

Total fresh substrate: 30 tons per hectare.

The simple crushing technology provides:

• Total Solid: 16% t ST / TT

• Total digestible sugars: 84%

• Total Ashes: 2,8%

• Total organic content: 97,2% tSV/ tST

These physical compound allows to estimate the

biogas yield of sugar juice, which is made by mainly

carbohydrate and has at very fast rate digestion:

Table V. Sugar Juice digestion data

The second substrate obtained from sugar stalks

crushing system is the solid bagasse. The bagasse

together with leaves and panicles represent the most

energetic content in terms of anaerobic digestion

potentials with a valuable nutrient content of about 4-5

kg/m3

Biogas yield of carbohydrates fibre: 790 l/kgSV

Methane related yield: 50 %


726

The Solid biomass substrate presents the following

parameters:

Bagasse + leaves + panicles: 34,8 fresh tons

• Total solid biomass: 50% tST/TT

• Ashes: 9%

• Organic Biomass: 91% tSV/ST

• Diluited with sugar juice digestate

The total Amount of biogas production and related

methane concentration is estimated below:

Table VI. Bagasse digestion data

Cubic meters of Biogas 550 m3

biogas/tSV

Methane related yield 60%

3 BIOGAS PRODUCTION YIELD and MIXING

SUBSTRATE PRODUCTION

The two substrates ( Juice based and bagasse based)

need to be integrated with liquid substrates in order to

reduce the solid content and to increase the digestion rate.

The concept is based on the integration of cow sludge

and water in both of the substrate in different

concentration.

3.1. Sugar Juice Based Substrate Production An Biogas

Yield Estimation

Sugar juice solid content is 16%. The aim is to reduce

the total amount of solid content up till 10% in order to

be digested in a semi-liquid reactor already used for

many biogas installation.

The table below shows the energy efficiency of Sugar

Juice:

Table VII. Sugar Juice biogas yield

Sugar Juice: 30,15 fresh tons

Solid Biomass: 4,82 tons

Organic Biomass: 4,69 tons

Biogas yield: 483 m3 Biogas/t SV

Toal biogas per ha: 2264,68 m3/ha

Sugar Juice is mixed with water and sludge in order

to reduce the total solid content from 16 to 10%. The

amount of sludge will also increase the biogas production

due to a solid content of 0,4 ST/TT.

In the table below the total substrate estimated for 25

hectares:

Table VIII. Sugar Juice mixture details

Total Sugar Juice (0,16): 753,75

Total Water (0) : 301,5

Total Sludge (0,04): 150,75

Total fresh tons : 1206

Mixture total solid: 0,105

The total amount of 1,206 fresh tons (=cubic meters)

will be processed in a thermophilic reactor at 55°C for

ten days.

The total percentage of cow slurry put in the digester

is 20% of juice, while the percentage of water is 40%.

The different substrates (Sludge and Juice, has different

biogas potentials, different solid content but a common

methane concentration of 50%.

Sludge biogas potential and methane concentration

estimated for this study are:

• Biogas potential: 400m3 biogas/ tST

• Methane concentration: 50%

The mixed substrate biogas potential has been

estimated with a total Biogas production estimation for

25 hectares from sugar juice:

Table IX. total biogas production from sugar juice

mixture

Total biogas from juice: 56614 m3

Total biogas from sludge: 2.412 m3

Total biogas production: 59.026 m3

Total Methane production: 29.513 m3

3.2. Bagasse Based Substrate Production And Biogas

Yield Estimation

Bagasse + leaves + panicles provide a total of 34,8

fresh biomass at 50% moisture. The objective is to reduce

the solid content to 20-22% of Moisture in order to digest

the biomass in a semi-solid reactor.

The solid biomass biogas yield is the following:

Table X1. Bagasse biogas yield

Total fresh biomass: 34,8 t/ha

Total Solid 17,4 t/ha

total volatile 15,834 t/ha

Total biogas 8708,7 m3/ha

Solid bagasse is mixed with slurry, water and a high

percentage of digested juice (5% solid) to reduce the

solid content from 45% to 21%. The table below shows

the final substrate components:


727

Table XI. Bagasse mixture details

Total Bagasse (0,45) 870 t

Total Water (0) 435 t

Total Sludge (0,04) 261 t

Digested Sugar Juice (0,05) 609 t

Total: 2175 t

Mixture total solid 0,21%

The total concentration of different substrate mixed

with bagasse is ìthe following:

• Water: 50% of solid biomass

• Sludge: 30% of solid biomass

• Sugar Juice digestate: 70% of solid biomass

Considering Sludge to have the same energy potential

defined above, the total energy provided by the anaerobic

digestion of bagasse based mixture substrated is:

Table XII. Biogas production from bagasse mixture

Total Biogas from bagasse: 217.718 m3

Total Biogas from sludge: 4.176 m3

Total biogas production: 221.894 m3

Total methane production: 132.719 m3

The substrate of 21% solid is digested in a two stages

thermophilic semi-solid reactor. The two stages are

represented by a first hydrolyser in micro-aerobic

conditions with general losses of about 3% in 2-3 days

retention time, and a second digester where the substrate

must remain for 35 days at 55°C.

4 DIGESTION LOGISTIC. ENERGY PRODUCTION

& ELECTRIC POWER INSTALLATION. (see the

scheme illustrated in Image 1 at the end of the paper)

The different substrate are connected with pipeline in

order to mix sugar juice digestate with the bagasse in the

second semi-solid digester. However, the digestion time

and the impossibility to store the sugar oblige to digest all

the milled sugar immediately.

4.1. Sugar Juice

The previously mentioned harvesting time of 50

days, and the very low retention time of 10 days due to

the high digestibility of the juice allows to reduce the

digester dimensions. The total cubic meters are 1,206. To

be divided in 5 times due to the possibility to harvest in

50 days what can be digested in 10 days.

Here below the data concerning digester dimension

for juice-based substrate

Table XIII. Sugar juice biogas digester and storage tank

Digester dimensions 251 m3

Storage tank: 460 m3

Tank for water 420 m3

The estimation above are calculated basing on the

installation of a CHP engine with 52% efficiency for

thermal energy production and 32% efficiency of electric

engine. The total amount of hours per year working of the

engines is very low, due to the need to process all a big

part of the biogas produced in 60 days.

The sugar juice digester is a thermophilic down-right

digester with 4 meters radius and 5 meters high. For a

total of 250 cubic meters

The total electric power is 68 kWe.

However, two solutions are under estimation:

• Utilization of biogas to produce heat and supply

the required thermal energy for digestate

drying, digesters heat demand etc..

• Store the biogas onsite mixing the biogas with

the amount of biogas produced by the other

digester.

4.2 Bagasse

The total amount of Solid substrate (21,1%) is 2,175

fresh tons per year. Part of this substrate is represented by

Sugar Juice digestate, which is recirculated in a pre-

hydrolyser and than in the semi-solid digester with a 70%

of bagasse input.

The sugar losses during hydrolisys retention time of

2days are estimated to be around 2-3%. (Wellinger et al.,

1999; Capela et al., 1999). Thus it is not considered as

affecting the biogas yield. The total of digested sugar

juice is so about 609 fresh tons per year (mix of water,

juice and slurry). This digestion will take place during all

along the year and the digestion retention time is

estimated to be around 35 days, thanks to the pre-

hydrolysis, the mix of sugar juice and a 55°C of

thermophilic digestion.

Here below a table with the parameters defined for

digester volume calculation.

Table XIV. Solid bagasse digestion parameters

Temperature 55°C

Retention time (thermophilic) 35 days

substrate heating capacity 4 Kj/kg K

Temperature substrate 12°C

The digester, as well as the hydrolyser is very small

consutruction insulated on lateral and base surface in

order to maintain the thermophilic temperature inside.

The reactor is a dry solid horizontal cylinder of 8 meters

length and 3 meters radius (total 226 cubic meters).


728

Table XV. Bagasse digester and storage tank

Digester dimensions: 226 m3

Storage Tank: 240 m3

Hydrolyser: 230 m3

The Hydrolyser is a downright micro-aerobic digester

with a high of 3 meters and a basis of 5 meters radius.

The Electric power engine is a CHP for raw biogas

internal combustion with 35% electric efficiency and

52% thermal efficiency.

The total estimated electric power is: 63kWe

4.3. Total Amount of energy production.

The methane produced from the two digesters is used

to produce electricity and heat. Here below the total

energy production estimation:

Total Energy production: 1.541.201kWh

Total Heat production: 847.661kWht

Total Electricity: 493.184kWhe

The electricity produced with two engines of 68 and

63 kWe is mostly sold to the national grid (estimated feed

in tariff 0,14 €/kWh)

The total heat produced is used all for the digesters

heating and for the bio-fertilizer production.

5 ANAEROBIC DIGESTER HEATING, DIGESTATE

DRYING SYSTEM AND MECHANICAL

SEPARATION ENERGY DEMAND:

The energy demand for heating tanks and moving

pumps, mechanical conveyor, etc represents a large part

of total thermal energy produced.

5.1 Digesters heat demand

The total amount of substrate to be heated is 2,772 m3

The heat demand has been calculated as follows:

Total mass: 2,772 m3

Total KJ/Kg K of substrate: 4

Total T : 55°C (thermophilic) – 12°C(T of substrate)

The total heat required by the digesters is:

2,772 m3 ×××× 4 KJ/Kg K ×××× (55°C-12°C)××××1,3

• Juice digester required heat: 74.906,00 kWht

• Bagasse digester required heat: 135.091,67 kWht

The Total thermal energy required for digester heat

supply is about 300,000 kWht per year.

5.2 Digestate treatment electricity demand.

In order to reduce the thermal energy required for

digestate drying activity, a mechanical conveyor for the

separation of a large part of water would be utilized.

It is estimated that the mechanical separation

consume about 1,4 kWhe per ton of fresh substrate, the

total consumption is around 3880 kWhe.

Through the mechanical separation, the water content

can be reduced from 90% to 50%, in the solid part, while

the liquid part contain 0,02% of solid.

The liquid part can be evaporated to recover all the

solid matter, or used as water supply for digester,

irrigation or other purposes. The recommendation is to

use the liquid as liquid part to be put in the digester, in

order to reduce the environmental impact of water

utilization.

A further amount of electricity must be considered

for the biofertilizer production, and for the total

electricity supply on site (cooling, other pumps, light,

etc..

According to the literature, a total amount of 10% of

electricity produced is considered to be used to feed all

the utilities of the biogas plant and biofertilizer

production installation.

For a total consumption of: 53,199 kWhe per year

5.3 Heat required for digestate drying system

After the mechanical separation, the digestate has a

50% moisture content. The objective is to reduce the total

moisture up till 10% -15% in order to be able to store the

biofertilizer.

The drying system consumption is about 800 kWht

7ton of water to evaporate.

Basing on this data, the total amount of heat required

has been calculated evaluating the total amount of water

to evaporate, which is 390 ton per year.

The result is: 312,362 kWht to be used for digestate

drying system

Considering the total heat demand required by Biogas

plant facility, the total amount of heat is:

Table XVI. Heat required by digesters and drying

systems

Drying required heat: 312,362 kWht

Digester required heat: 74,906 kWht

Digester required heat: 135,091 kWht

Total Heat Required: 522,360 kWht

The resulting remaining energy available is shown in

the table below:

Table XVII. Total Remaining Net Energy

Total remaining heat: 279,064 kWht

Total remaining electricity: 439,985 kWhe


729

6 THE PRODUCTION OF BIOFERTILIZER

6.1 Sweet Sorghum digestate available nutrients

The Nitrogen content in Sweet Sorghum digestate is

estimated to be around 4% (literature). The digestate

solid content ratio on fresh cubic meters output is

underestimated to 10% (16% is the solid content of

bagasse digestate, 5% is solid content of sugar juice

digestate). The theoretic output should be considered

around 13% but an underestimation have been considered

in order to include drying losses, liquid part separation

etc..

The percentage of Nitrogen is always considered as

50 kg/m3 of dry matter (10% solid).

The total amount of fresh biomass output is: 2,716

tons per year. The estimated solid content, as mentioned

above, is 10%.

With 25 hectares, nitrogen results to have a total

amount of 13.582 tons per year.

150 kg of N per hectare per year are required for

Sweet Sorghum Cultivation

The total is 3850kg of N = 3.8 tons/year for

cultivation.

The total remaining biofertilizer for sale is 196 tons,

with a N percentage of 5%. The price has still to be

estimated.

The NH4-N content is 70-80% of total organic N

thanks to the anaerobic digestion process, this make the

substrate a more valuable fertilizer with fast absorption

rate of N in the soil. Furthermore, the total P is 0,8 kg/m3

of fresh biomass. The recycling of Phosphorus (up till

90%) makes this biofertilizer very attractive in terms of

cultivation sustainability. Of course a valuable production

and control system is included in the biofertilizer plant

installation. The different steps for evaluating the

Digestate nutrient content is:

• Total Nitrogen(TN) persulfate digestion, colorimetric

method

• Total Ammonia Nitrogen (TAN) was measured with

an ion-selective electrode

• Phosphorus persulfate digestion, colorimetric method

• Potassium was measured with an ion-selective

electrode

In addition a new technique would be applied in

order to increase the digestate nutrient content and

provide a real high value biofertilizer (Estimated up till 6-

7% N):

6.2 New technology for biofertilizer production:

New systems based on bacteria and fungi inoculation

highly increase biofertilizers nitrogen content. The

sustainability of biofertilizer derives mostly from the

Phosphorus content. The production of fertilizer fom

digestate include the recirculation of Phosphorus, which

is one of the most importan nutrinet in nature. It is thus

very important to concentrate the attention on the

increase of Nitrogen content of substrate. The technology

identified is the following:

Integration of anaerobic digestion technology improving

digestate nutrient content with inoculation of cellulolytic

fungi (T. harzianum )and Azotobacter (or Azospirillium)

for highest value biofertilizer production. [2]

Incoulation data source: Bayani M. Espiritu

Figure 2. Bio-Fertilizer Production Concept Scheme

In addition, A new pelletization machinery has been

created by a consortium of industries and investors which

is able to pelletize biomass with very high moisture

content (trials with peat have been made)

This machine operates at about 80°C, this process

avoids ammonia losses and reduce pelletization costs.

7 COSTS, INCOMES & ESTIMATED RETURN OF

INVESTMENT

7.1. Estimation of costs

The total investment has been evaluated considering

the following values:

Table XVIII. Biogas plant components cost

Digester price 180 €/m3

Engine Price 800 €/kWe

Insulation digester lateral

surface (s=0,06):

400 €/m3

Insulation digester basis

(s=0,08)

200 €/m3

Heating system connection 1500 €

pipeline for substrate : 4,5 €/m

Pressure pump (5,5 kWe) 2800 €/each

Secure Flame (>400kWt) 10000 €/each

Electricity connection 20,000 €

Annual Maintenance (% total

costs)

1,5 % total

The total digesters cost has been calculated

considering the two tanks, the bagasse storage tank, and

the hydrolyser. The average cost for this type of digester

is 190 €/m3. While the sugar juice tank has been defined

as cheaper because of it is designed without a heating

system and without post-digestion biogas storing system.

The final cost of this tank is defined as 120 €/m3.

Internal combustion engines cost is estimated to be

aroung 850 €/kWe installed power for both the engines.

The efficiency is estimated to be quite low (32%) due to

the small size of the engines.

In addition, lateral surface insulation cost is estimated

to be 5,802 €, while the basis of the sugar juice digester

insulation is 1,256 €.

Here below a resuming table including all the costs

estimated for digester and power engines installation. The

cost of harvesting machineries and utilities has not been


730

evaluated in this study due to the general idea that this

type of installation should be integrated in a pre existing

farm.

Table XIX. Total estimated investment costs

COSTS

Digester 178.980

Engine 111.510

Sugar juice storage tank 55.200

Insulation: 7.059

Heatin system connection: 1.500

Pipeline: 4.000

Secure flame: 10.000

Pumps: 8.400

Electricity grid connection: 20.000

Fertilizer plant cost: 30.000

Total: 426.649

7.2. Estimation of Incomes

Three different main products are salable on the

market every years from this type of biogas plant:

o Electricity

o Sweet Sorghum Grains

o Bio-Fertilizer

Electricity: Net electricity produced is estimated to be

493.184 kWhe per year, divided between the two

different Internal combustion engines operating

independently.

The estimated Feed in tariff in Belgium is not so

high. The average is 12-15 €/kWhe for those biomass

plant operating with residues, using CHP engines, fully

sustainable. These parameters match perfectly the

operating conditions of Sweet Sorghum co-production of

Biogas and Biofertilizer.

The average feed in tariff identified is defined as 0,14

€/kWhe. For a total annual income of 61,598 €/year.

Grains: Grains for animal feed: Sweeto Sorghum grains

are rich of sugar and can be used as feedstock for

different utilizations. Sugar market can easily produce

valuable sugar from grains. In additions, sweet sorghum

grains’ nutrient content makes them a valuable product to

be sold as animale feed.

The average low price for a new market is estimated

around 230 €/ton (0,23 €/kg). With a general yield of 5,4

tons of grains per year, the income from grains sale is

29700 €/year.

Biofertilizer (see the impact of Artificial fertilizer in the

images 2 and 3 at the end of the paper): Biofertilizer

market is acomplicate issue to solve in Europe. Even if

bio-food and sustainable agriculture strongly require the

application of a natural fertilizer with the possibility to

recirculate phosphorus in the soil, there are many barriers

to overcome in terms of permissions and directive.

Currently the utilization of digestate for the

production of valuable fertilizer is not permitted in

Europe. This create problems to farmers who decide to

start with the installation of a biogas plant because often

they do not have enough land where to spread the

digestate.

Digestate treatment and inoculation of bacteria and

funghi is a well known technology which allow to

increase a lot the nitrogen content of the substrate

enhancing the fertilizer properties.

Here in this study, the biofertilizer production is just

illustrated in terms of technology, but even if the

estimation for N percentage in weet Sorhum digestate is

considered as 5% (60-80% NH-N), the price is very very

low.

So, the market price is 0,15 €/kg. For a total income

of about 29,400 €/year.

With these three sources of income, the total annual

potential is shown in the table below:

Table XX. Total estimated incomes

INCOMES

Electricity 61.598

Grains 29700

Fertilizer 29,400

Total: 120.698

It is so easy to calculate the return of the investment

for this pre-feasibility study:. With an investment of

426,000 € and a general annual income of 120,698 €, the

estimated return of the investment for Sweet Soeghum

biogas plant is defined as

3 years and 6 months.

8 CONCLUSION

This paper refers to a pre-feasibility study for a

demonstration plant in Belgium. Many data concerning

the costs, the incomes and other activities energy

consumption have been calculated in order to increase

provide an overestimation for the investment.

Next steps of this study will be focused on:

Contacting Wallon region and discuss terms of

collaboration for a demonstration plant which would be

able to sell biofertilizer produced evaluating also a fixed

feed in tariff for the electricity for sale.

Testing in laboratory scale the yield of Sweet

Sorghum anaerobic digestion concept in order to verify

the good amount of biogas and biomethane concentration

(underestimated for sugar juice)

Studying biofertilizer production technique (already

used for compost) on anaerobic digestate and estimate the

price according to a deep the market survey.

EUBIA intends to work next to regional and national

authorities in order to define a new biofertilzer market for

refined digestate, creating standardization parameters,

certification schemes thus establishing a new strategy for

a pro-biofertilizer European market.


731

Figure 3. Anaerobic digestion of Sweet Sorghum concept Scheme (1)

Figure 4. Artificial Fertilizer high environmental Impact (1)


732

Figure 5.Artificial Fertilizer High Environmental Impact (2)


733

for biogas and high value biofertilizer production · pdf filefor biogas and high value...

Documents