Benefits and risks of applying compost to European soils Luca Montanarella

1. Benefits and risks of applying compost to European soils Luca Montanarella

2. Status of Soil Organic Carbon in European soils: Spatial data layer of estimated OC contents in the surface horizon of soils in Europe (30cm), 1km grid size.

3. Terrestrial organic carbon pool Max. potential carbon stock at climax Max. potential carbon stock achievable through LULUCF measures Actual terrestrial carbon stock Terrestrial carbon stock depletion by historical human induced LULUCF activities Hypothetical carbon stock build-up by LULUCF measures Soil Organic Carbon dynamics time Ca. 60,000 B.C. to 1000-1500 A.DLast “green” revolutionpresentfuture

4. Monitoring SOM on Broadbalk, Rothamsted %OC FYM FYM since 1885 FYM since 1968 NPK No fertilisers or manures Goulding FYM applied at 35 t ha-1 yr-1

5. Carbon Sequestration Rate, CSR Potential Carbon Sequestration, PCS Carbon Loss Rate, CLR Potential Carbon loss, PCL (Risk assessment) Soil specific carbon sequestration potential tC Max tC Max & Min tC are soil specific Actual tC Min tC Years

6. SOC content is depending on humidity, temperature, soil type and land use Example: Change in organic carbon content of topsoils in England and Wales [after Loveland, NSRI, Cranfield University, Silsoe]

7. 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).

8. Total biowaste and green waste arising in the European Union (1,000 t/y) 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. • (*) Biowaste of industrial origin; (**) Catalonia; (***) Belgium total; (****) Italy: CIC and Italian Environmental Agency data for 2002.

9. Microorganisms -OH Soil organic matter Origin Turnover Complexity Corg CO2 Decomposing fresh OM (Particulate organic matter) soluble OM Colloidal OM Polysaccharides and biomolecules Humic substances

11. Potential measures for cropland Freibauer et al. 2003

12. -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).

13. European Climate Change Programme ECCP 2000-2001 Total carbon sequestration potential of measures for increasing soil carbon stocks in agricultural soils for Europe (EU15) and limiting factors.

14. Comparative rates and loads of Cu inputs into French soils TWG Organic Matter

17. 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.