Benefits and risks of applying compost to European soils Luca Montanarella 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. Soil Organic Carbon dynamics 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 time Ca. 60,000 B.C. to 1000-1500 A.D Last “green” revolution present future Monitoring SOM on Broadbalk, Rothamsted %OC 3 2.5 Management/vegetation Old pasture (8-18cm) Old woodland (13-18cm) Broadbalk, after 50 years continuous wheat, 1893 No manure since 1839 (0-23cm) Complete minerals and 185kg (NH 4)2SO4 most years since 1843 14 tons of farmyard manure annually since 1843 (0-23cm) %C 1.5 2.4 0.9 1.1 FYM 2.2 FYM since 1885 2 1.5 FYM since 1968 NPK 1 No fertilisers or manures 0.5 FYM applied at 35 t ha-1 yr-1 19 90 19 70 19 50 19 30 19 10 18 90 18 70 18 50 0 Goulding Soil specific carbon sequestration potential Max & Min tC are soil specific tC 100 Max tC 90 80 70 60 Actual tC50 40 30 20 10 0 Min tC 0 5 Carbon Sequestration Rate, CSR Potential Carbon Sequestration, PCS Carbon Loss Rate, CLR Potential Carbon loss, PCL (Risk assessment) 10 15 20 Years 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] 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). Total biowaste and green waste arising in the European Union (1,000 t/y) •Country •Austria •Municipal solid waste production •4 110 •Biowaste actually collected •Greenwaste actually collected •880 •850 •Biowaste potentially collectable •Greenwaste potentially collectable •1 220 •1 020 •(*) 580 •BelgiumFlanders •(***) 4 781 •BelgiumWallonia •900 •120 •160 •12 000 •14 000 •48 715 •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 •27 000 •(****) 1 100 •/ •9 000 •1 848 •/ •/ •440 •Ireland •Luxembourg Modified for France by I. Feix. Data from Germany are from the report Bundesgütegemeinschaft Kompost: Verzeichnis der Kompostierungs- und Vergärungsanlagen in Deutschland, 2003. •390 •Germany •Italy 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. •330 •299 •30 •60 •Netherlands •8 480 •1 500 •800 •Portugal •3 600 •/ •10 •Sweden •3 998 •130 •150 •United Kingdom •28 989 •39 •860 •European Union •176 303 •15 854.3 •2 500 •1 000 •1 300 •970 •530 •3 200 •54 806 •(*) Biowaste of industrial origin; (**) Catalonia; (***) Belgium total; (****) Italy: CIC and Italian Environmental Agency data for 2002. Soil organic matter Origin Turnover Complexity Corg CO2 Decomposing fresh OM (Particulate organic matter) soluble OM -OH Colloidal OM Polysaccharides and biomolecules Humic substances Microorganisms Model of soil carbon dynamics Vegetation, organic input Primary production, quality CELL Soil, Land Use, Climate (structural polysaccharides) 0.3 yr LIGNIN LABILE 2.5 yr 0,87 yr microbial synthesis mineralization CO2 HUM (humic and protected) CO2 25 yr numerical values for soil/land use = - 20% clay - temperature 12°C - water/porevolume > 0,4 - annual crops conv. tillage STABLE 3300 yr CO2 Balesdent, 2000 Potential measures for cropland 0 1 2 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 Freibauer et al. 2003 3 4 5 6 7 t C/ha/y 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 agroindustrial 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). 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. Comparative rates and loads of Cu inputs into French soils 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 1 to 4% 334 0.668 165 MSW compost 0.1% 164.4 0.822 47 Greenwaste compost 0.2% 50.8 0.254 14 Households 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.) P fertilisers 80-90% / 0.004 102 ~3% (vineyards & arboriculture) / 0.8 to 14 752 to 13 152 100% / 0.006 to 0.015 185 to 462 Urban sewage sludge Biodegradable wastes Agricultural practices Cu fungicides Atmospheric depositions TWG Organic Matter biowaste Fig. I.1: Heavy Metal Contents in European Soils according to Soil Parent Material and Land Use - Cadmium - Fig. I.3: Heavy Metal Contents in European Soils according to Soil Parent Material and Land Use - Copper - Map Sources: European Soil Data Base, Version 1.0 CORINE Land Cover, Version 12/2000 Status June 2003 Classes of Cu Content [mg/kg] - Median values - Map Sources: European Soil Data Base, Version 1.0 CORINE Land Cover, Version 12/2000 Status June 2003 Classes of Cd Content [mg/kg] - Median values - 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.