Benefits and risks of applying compost to European soils

Luca Montanarella

Spatial data layer of estimated OC contents in the surface horizon of soils in Europe (30cm), 1km grid size.

Status of Soil Organic Carbon in European soils:

Hypothetical carbon stock build-up by LULUCF measures

Actual terrestrial carbon stock

Max. potential carbon stock achievable through LULUCF measures

Max. potential carbon stock at climax

Terrestrial organic carbon pool

Terrestrial carbon stock depletion by historical human induced LULUCF activities

Ca. 60,000 B.C. to 1000-1500 A.D Last “green” revolution present future

time

Soil Organic Carbon dynamics

Monitoring SOM on Broadbalk, Rothamsted

%OC

0

0.5

1

1.5

2

2.5

3 FYM

FYM since 1885FYM since1968

NPK

No fertilisers or manures

FYM applied at 35 t ha-1 yr-1 Goulding

Management/vegetation % C

Old pasture (8-18cm) 1.5Old woodland (13-18cm) 2.4

Broadbalk, after 50 yearscontinuous wheat, 1893

No manure since 1839 (0-23cm) 0.9

Complete minerals and 185kg

(NH4)2SO4 most years since 1843

1.1

14 tons of farmyard manureannually since 1843 (0-23cm)

2.2

Soil specific carbon sequestration potential

0

1020

30

4050

60

70

8090

100

0 5 10 15 20

Max tC

Min tC

Actual tC

Max

& M

in t

C a

re

soil

sp

ecif

ic

Years

tC

Potential Carbon Sequestration,

PCS

Carbon Sequestration Rate, CSR

Potential Carbon loss, PCL (Risk

assessment)

Carbon Loss Rate, CLR

SOC content is depending on humidity, temperature, soil type and land use

[after Loveland, NSRI, Cranfield University, Silsoe]

Example: Change in organic carbon content of topsoils in England and Wales

Carbon losses from all soils across England and Wales 1978-2003(Bellamy et al., Nature Sep 2005, based on ca. 6000 samples, 0-15cm)

Bellamy et al. estimate annual losses of 13 million tonnes of carbon. This is equivalent to 8% of the UK emissions of carbon dioxide in 1990, and is as much as the entire UK reduction in CO2 emissions achieved between 1990 and 2002 (12.7 million tonnes of carbon per year).

•Country •Municipal solid waste production

•Biowaste actually collected

•Greenwasteactually collected

•Biowaste potentially collectable

•Greenwaste potentially collectable

•Austria •4 110 •880•(*) 580

•850 •1 220 •1 020

•Belgium-Flanders

•(***) 4 781 •330 •390 •900

•Belgium-Wallonia

•120 •160

•Germany •48 715 •12 000 •14 000

•Denmark •2 787 •280 •490 •50 •550

•France •21 100 •74.7 •860.6 •9 006 •5 900

•Finland •2 100 •100 •600

•Spain •14 296 •(**) 60 •/ •6 600

•Greece •4 200 •/ •/ •1 800

•Italy •27 000 •(****) 1 100 •/ •9 000

•Ireland •1 848 •/ •/ •440

•Luxembourg •299 •30 •60

•Netherlands •8 480 •1 500 •800 •2 500 •1 000

•Portugal •3 600 •/ •10 •1 300

•Sweden •3 998 •130 •150 •970 •530

•United Kingdom

•28 989 •39 •860 •3 200

•European Union

•176 303 •15 854.3 •54 806

•(*) Biowaste of industrial origin; (**) Catalonia; (***) Belgium total; (****) Italy: CIC and Italian Environmental Agency data for 2002.

J. Barth, An estimation of European compost production, sources, quantities and use, EU Compost Workshop “Steps towards a European Compost Directive”, Vienna, 2-3 November 1999.

Modified for France by I. Feix. Data from Germany are from the report Bundesgütegemeinschaft Kompost: Verzeichnis der Kompostierungs- und Vergärungsanlagen in Deutschland, 2003.

Total biowaste and green waste arising in the European Union (1,000 t/y)

Soil organic matter

OriginTurnoverComplexity

Decomposing fresh OM(Particulate organic matter)

Microorganisms

Colloidal OM Polysaccharides and biomoleculesHumic substances

soluble OM

-OH

CO2Corg

CELL(structuralpolysaccharides)

HUM(humic

and protected)

STABLE

mineralization

microbialsynthesis

0.3 yr

LIGNIN

2.5 yr

LABILE

0,87 yr

25 yr

3300 yr

numerical values forsoil/land use =- 20% clay- temperature 12°C- water/porevolume > 0,4- annual crops conv. tillage

CO2

CO2

CO2

Vegetation, organic input

Primary production,quality

Soil, Land Use,Climate

Balesdent, 2000

Model of soil carbon dynamics

Potential measures for cropland0 1 2 3 4 5 6 7

Zero-tillage

Reduced-tillage

Set-aside

Grasses and permanent crops

Deep-rooting crops

Animal manure

Crop residues

Sewage sludge

Composting

Improved rotations

Fertilisation

Irrigation

Bioenergy crops

Extensification

Organic farming

t C/ha/y

Freibauer et al. 2003

Measure Potential soil C sequestration rate (t CO2.ha-1.y-1)

Estimated uncertainty (%)

Ref. / notes

Limiting factor Soil sequestration potential (106 CO2.y

-1) given

limitation

Ref. / notes

Animal manure

1.38 > 50% 1 Manure available = 385.106 t dm.y-1

86.83 4

Crop residues 2.54 > 50% 1 Surplus straw = 5.3.106 t dm.y-1

90.46 5

Sewage sludge 0.95 > 50% 1, 2 Sewage sludge available in the mid-time (2005) = 8.3.106 t dm.y-1

6.30 6

Composting 1.38 or higher >> 50% 3, 2 Potential production of composted materials present in MSW = 13 to 22.106 t dm.y-1. Figures include processing of biowaste from agro-industrial by-products, but neither manure, nor crop residues.

11 7

-1. Smith et al. (2000); per hectare values calculated using the average C content of arable top soils (to 30 cm) of 53 t C.ha -1; Vleeshouwers and Verhageb (2002), cf. table 5.-2. The sequestration values are based on a load rate of 1 t ha -1.y-1, which was the lowest safe limit in place (in Sweden) at the time of analysis for this figure (1997). A higher loading rate would give a higher sequestration rate per area. As the limiting factor for the application of compost is the amount of producible compost, a higher loading rate on a certain area would imply that a more limited area could be treated.-3. Assumed to be the same as animal manure figure of Smith et al. (2000).-4. Total figure for EU15 calculated from figures in Smith et al. (2000). Total amount of manure available from Smith et al. (1997).-5. Total figure for EU15 calculated from figures in Smith et al. (2000). Total amount of surplus cereal straw available from Smith et al. (1997).

Total carbon sequestration potential of measures for increasing soil carbon stocks in agricultural soils for Europe (EU15) and limiting factors.

European Climate Change Programme ECCP 2000-2001

Land surface (%UAA)

Mean level of Cu (mg.kg-1 dm)

Cu rates(kg.ha-1.y-1)

Cu annual loads (t.y-1) over

France

Urban sewage sludge 1 to 4% 334 0.668 165

MSW compost 0.1% 164.4 0.822 47

Biodegradablewastes

Greenwaste compost 0.2% 50.8 0.254 14

Households biowaste compost

0.02% 87.8 0.439 1

Animal effluents 20-25% Ex.: 52 cattle; 730 pigs

0.7 cattle; 2.3 pigs

4 460 (all an. effl.)

Agriculturalpractices

P fertilisers 80-90% / 0.004 102

Cu fungicides ~3% (vineyards & arboriculture)

/ 0.8 to 14 752 to 13 152

Atmospheric depositions

100% / 0.006 to 0.015

185 to 462

Comparative rates and loads of Cu inputs into French soils

TWG Organic Matter

Map Sources:European Soil Data Base, Version 1.0CORINE Land Cover, Version 12/2000

Status June 2003

Classes of Cu Content[mg/kg]

- Median values -

Fig. I.3: Heavy Metal Contents in European Soilsaccording to Soil Parent Material and Land Use

- Copper -

Map Sources:European Soil Data Base, Version 1.0CORINE Land Cover, Version 12/2000

Status June 2003

Classes of Cd Content[mg/kg]

- Median values -

Fig. I.1: Heavy Metal Contents in European Soilsaccording to Soil Parent Material and Land Use

- Cadmium -

Conclusions• Soil Organic carbon levels in Europe are low and are constantly

declining.• There is the urgent need to reverse this negative trend• Compost and bio-waste could provide a valuable source of

organic matter for European soils.• Long-term fate of the exogenous organic material in soils needs

to be taken into account, depending on the pedo-climatic local conditions.

• Potential contamination of bulk organic materials, like compost, sludges and other bio-wastes is a potential threat to human health

• Careful application of QA/QC and of the precautionary principle is a pre-requisite for increased acceptance of these materials as soil improvers.