Day 10-1 Composting in DK PDF

12130 Solid Waste Technology and Management Charlotte Scheutz Composting in DK Introduction to composting in DK Gas emission measurements Central composting Home composting Environmental assessment 4 October 2024 DTU Sustain Composti...

12130 Solid Waste Technology and Management Charlotte Scheutz Composting in DK Introduction to composting in DK Gas emission measurements Central composting Home composting Environmental assessment 4 October 2024 DTU Sustain Composting in DK 1  1 Introduction Composting in Denmark Greenhouse gases 4 October 2024 DTU Sustain Composting in DK  Composting of organic waste Aerobic mineralisation and stabilisation of organic matter Generally a process with a quite low-energy input and with limited environmental impacts The biologically stabilised material (compost) is used all over the world for nutrient recycling and to increase the natural soil quality www.clearspan.com www.ecosetconsulting.com Christensen, 2010 4 October 2024 DTU Sustain Composting in DK  Organic waste in DK and EU Municipal organic waste – Garden waste Biowaste – Organic household waste (OHW) The amount of (collected) garden waste has more than doubled during the last 20 years in Denmark The amount of biowaste has increased by 10% (EU) Landfill directive; ban on landfilling of biowaste in EU, but still 40% of biowaste is being landfilled Increased need for treatment options incl. biological treatment options 4 October 2024 DTU Sustain Composting in DK  Composting of organic waste in DK I Input to central composting: – Organic household waste (OHW): 49 500 t pr yr (5% of total OHW) – Garden waste: 831 000 t pr yr (99% af total GW) – Sludge (107 000 t pr yr), park (220 000 t pr yr), and other organic wastes (21 000 t pr yr) Input to home composting: OHW: 21 000 t pr yr (estimate) 142 composting facilities; primarily windrow composting (131), mat composting (8), container composting (3) OHW has to be source separated – 9 facilities, which receives OHW 4 October 2024 DTU Sustain Composting in DK  Composting of organic waste in DK II Very different operational practices (windrow layout, turning, stabilization, maturation period) Typical production is 0,4 t compost per 1 t input material Limit values for metals, organic compounds, and pathogens when using composted OHW (sludge) on land Restrictions for using OHW on land. Danish legislation: 55ºC for 2 weeks or 1 hour at 70ºC No restrictions for using composted GW on land Compost is used primarily in private gardens (45%), agriculture (20%), green areas (10%) and landfill covers (10%), etc. 4 October 2024 DTU Sustain Composting in DK  GHG emissions from composting Composting results in emissions of GHGs – how much is not known very well GHGs are molecules that absorb and emit infrared radiation Accumulation of GHGs in the atmosphere cause climate change Greenhouse gas emissions from composting:  CO2  GWP of 0 (biogenic carbon)  CH4  GWP of 28  N2O  GWP of 265 IPCC, 2013 IPCC 4th Assessment Report, 2007 4 October 2024 DTU Sustain Composting in DK  Research objective To quantify the gas emission using a method that captures the whole gas emission from windrow composting We have performed GHG emission measurements at three Danish windrow composting facilities: – Aarhus composting plant treating garden/park waste, – Fakse composting plant treating garden/park waste mixed with sewage sludge, and straw – Klintholm composting plant treating garden/park waste and organic household waste. 4 October 2024 DTU Sustain Composting in DK  2 Measurements of gas emissions from central composting Central composting – three windrows facilities Measurement method Emission factors 4 October 2024 DTU Sustain Composting in DK  Aarhus composting facility Garden and park waste 15,500 Mg per year 8-12 windrows 115 m long, 9 m wide and 4 m high Composting time is 10 to 14 month Turning frequency is once a month 4 October 2024 DTU Sustain Composting in DK  Compost temperature and gas composition Andersen et al., I 4 October 2024 DTU Sustain Composting in DK  Composting temperature Temperature development in compost pore space 4 October 2024 DTU Sustain Composting in DK  Compost gas composition 4 October 2024 DTU Sustain Composting in DK  Gas flow in windrows Measurements with small flux chambers Chimney effect  gases escape through the top of the windrow Reason for choosing the small- scale measurement methods 4 October 2024 DTU Sustain Composting in DK  Comparison of small-scale methods A method which measures the emission from the whole compost windrow system is needed for proper quantification! 4 October 2024 DTU Sustain Composting in DK  Dynamic tracer dispersion method – single tracer approach Mobile instumentation 𝑝𝑙𝑢𝑚𝑒 𝑒𝑛𝑑 𝐶 𝑝𝑙𝑢𝑚𝑒 𝑠𝑡𝑎𝑟𝑡 𝑚𝑒𝑡 ℎ𝑎𝑛𝑒 𝐶𝑚𝑒𝑡 ℎ𝑎𝑛𝑒 𝑏𝑎𝑐𝑘𝑔𝑟𝑜𝑢𝑛𝑑 𝑑𝑥 𝑀𝑊𝑚𝑒𝑡 ℎ𝑎𝑛𝑒 𝐸𝑚𝑒𝑡 ℎ𝑎𝑛𝑒 𝑄𝑡𝑟𝑎𝑐𝑒𝑟 𝑝𝑙𝑢𝑚𝑒 𝑒𝑛𝑑 𝐶 𝑝𝑙𝑢𝑚𝑒 𝑠𝑡𝑎𝑟𝑡 𝑡𝑟𝑎𝑐𝑒𝑟 𝐶𝑡𝑟𝑎𝑐𝑒𝑟 𝑏𝑎𝑐𝑘𝑔𝑟𝑜𝑢𝑛𝑑 𝑑𝑥 𝑀𝑊𝑡𝑟𝑎𝑐𝑒𝑟 Trace gas release 4 October 2024 DTU Sustain Composting in DK  Dynamic tracer dispersion method – double tracer approach composting landfill Scheutz et al. (2011) Waste Management 4 October 2024 DTU Sustain Composting in DK  Stationary tracer dispersion method – single tracer approach Distance: N 2O CH4 6000 Plume transect 80 0.5-2 km from 60 source 4000 N2O (ppb) CH4 (ppb) 40 Tracer bottle and flow regulator 2000 20 0 0 1 4 :3 8 :2 4 1 5 : 0 7 :1 2 1 5 :3 6 :0 0 T im e Tracer source Mobile FTIR instrument (N2O) 4 October 2024 DTU Sustain tracer gas should be: Composting in DK - inert - it should noty dissolver in water - it shouldn’t be heavy  Requirements to application of the dynamic tracer dispersion method Gasses with long atmospheric lifetime Good/stable wind conditions (speed, direction, vertical mixing) Drivable roads/paths nearby and oriented Sensitive analytical instrument (high resolution, ppb range) and fast responding (seconds) 4 October 2024 DTU Sustain Composting in DK  Controlled tracer and methane release test Release of CH4 and C2H2 Measurement distances Tracer gas configurations Determination of methane/tracer ratios Plumes 350 m downwind 4 October 2024 DTU Sustain Composting in DK 20  Controlled tracer and methane release test Plumes: 350, 700 and 1200 m downwind Plume 3: 4.5 kg CH4 h-1 Plume 2: 5.2 kg CH4 h-1 Plume 1: 4.8 kg CH4 h-1 Controlled release: 4.7 kg CH4 h-1 CH4 (red) and C2H2 (yellow) concentration above background 4 October 2024 DTU Sustain Composting in DK  Quantification at Odense Landfill Composting Shredder Ash. Stigø – old landfill Mixed waste w. gas extraction = tracer placement 4 October 2024 DTU Sustain Composting in DK  Quantification at Odense Landfill 23 4 October 2024 DTU Sustain Composting in DK  Aarhus composting facility 4 October 2024 DTU Sustain Composting in DK  Fakse composting facility Garden waste (GW) Sewage sludge (SS) Mix garden waste, sewage sludge and straw 6,900 Mg GW per year 8,200 Mg SS per year 1,200 Mg straw per year 6 windrows 148 m long, 4 m wide, and 2 m high Composting time is 7 weeks Turning frequency is once a week 4 October 2024 DTU Sustain Composting in DK  Klintholm composting facility Garden waste (GW) Kitchen waste (KW) 11,000 Mg GW per year 3,300 Mg KW per year Garden waste: windrows of 9 m wide, and 5 m high composting time is 7 weeks and turning frequency is once a month Garden waste mixed with kitchen waste: windrows of 7 m wide, and 3.5 m high composting time is 7 weeks and turning frequency is every second week 4 October 2024 DTU Sustain Composting in DK  Total GHG emissions (kg h-1) Facility CH4 N2O CO2 CO Total GHG emission in CO2‐ eq.* Aarhus (2) 5.73  1.16 0.18  0.08 732  88 0.63  0.30 196 Fakse, windrow 0.50  0.25 0.06  0.03 332  166 n.a. 30 composting (1) Fakse, sludge 2.40  0.63 0.03  0.01 n.a. n.a. 69 pit (1) Klintholm (5) 4.56  0.82 0.08  0.05 n.a. n.a. 138 n.a.: Not analyzed. (n): number of campaigns. Note that CO2 is not included in the total GHG given in CO2-eq. 4 October 2024 DTU Sustain Composting in DK  from normalized results: Emission factors (kg Mg-1ww) Facility Waste input CH4 N2O Total GHG emission in CO2‐eq.* Mg ww yr‐1 kg Mg‐1 ww kg Mg‐1 ww kg Mg‐1 ww Aarhus (2) 15,500 3.24 0.10 111 Fakse, windrow 16,300 0.27 0.03 16 composting (1) Klintholm (5) 14,300 2.79 0.05 85 Amlinger et al., 2008 windrow composting biowaste 14‐41 Amlinger et al., 2008 windrow composting garden waste 6‐68 IPCC Default value 4 0.3 80 Andersen et al., 2010. Home 0.4‐4.2 0.3‐0.45 100‐239 composting Min‐Max 4 October 2024 DTU Sustain Composting in DK  Conclusion The tracer gas method was successfully used to quantify GHG emissions from windrow composting facilities Flux chambers underestimated the emissions Composting of organic waste generate GHG emissions in terms of CH4 and N2O Even small N2O emissions can be of importance due to the high GWP of N2O The GHG emissions varied between 30 and 196 kg CO2-eq. h-1 GHG emissions were influenced by type of organic waste, windrow dimensions, and turning frequency 4 October 2024 DTU Sustain Composting in DK  Measurements of gas emissions from home composting Home composting Measurement method Emission factors 4 October 2024 DTU Sustain Composting in DK  Introduction to home composting Home composting is an interesting alternative to centralized composting About 21 000 t household waste is home composted pr yr (estimate) in DK Home composting is a unique waste management option because the waste producer is also the processor and end-user of the product Microbial degradation of organic wastes entails the production of various gases such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and carbon monoxide (CO) Very few previous studies on gaseous emissions from home composting activities 4 October 2024 DTU Sustain Composting in DK  Research objective The main objectives of were to: 1. establish a representative single-family home composting system and 2. quantify the greenhouse gas (GHG) emissions to obtain reliable emission factors (EFs) from home composting of organic household waste 4 October 2024 DTU Sustain Composting in DK  The experimental setup – the composting units 6 composting units Addition of waste – 12 families – Food waste twice a week (by volunteers) – Garden waste (by authors) Operation – Two phases: composting (1 year), maturation (3 month) – Different aeration frequencies by manual mixing of the compost – After 1 year, high loads of waste were added to two units 4 October 2024 DTU Sustain Composting in DK  Input waste and mixing frequency 4 October 2024 DTU Sustain Composting in DK  Gas emission measurements 4 October 2024 DTU Sustain Composting in DK  Example of flux measurement Average R2 values for all measurements (98 per unit): 0.95 for CO2 0.95 for N2O 0.74 for CO 0.90 for CH4 4 October 2024 DTU Sustain Composting in DK  Temperature development Temperature development during home composting of OHW in Unit 1 during the composting and maturation phase 4 October 2024 DTU Sustain Composting in DK  GHG emissions 4 October 2024 DTU Sustain Composting in DK  Cumulative emissions 4 October 2024 DTU Sustain Composting in DK  GHG emission factors Mixed every week Note: Only CH4 and N2O Mixed every 6th week were included in the Total Not mixed EF 4 October 2024 DTU Sustain Composting in DK  Conclusion Home composting emits GHGs Emission factors were between 100 and 239 CO2-eq. Mg-1 ww input material Emission factors varied up to a factor of 2.5 in the present study (depending on the operation=mixing) Significantly higher CH4 emission from home composting units that were frequently manually mixed Total global warming emission factors are similar with those from centralized composting and numbers reported in another related study on home composting Very few previous studies on gaseous emissions from home composting activities 4 October 2024 DTU Sustain Composting in DK Environmental assessment LCI and LCA Central composting Home composting 4 October 2024 DTU Sustain Composting in DK  its difficult to study ammonia Environmental emissions from composting Emission of GHGs; CH4 and N2O Emission of NH3 Emission of leachate (C, P, N, metals) Emission of CO2, SOx og NOx from combustion of fossil fuel (shredding, sorting, moving, turning, size separation) Use on land – negative environmental impacts Leaching of N (NH4+ and NO3-) to surface water and groundwater Air N2O emission Accumulation of metals and organic compounds in soils Use on land – positive environmental impacts Substitution of nutrients (P,N,K), peat and lime C-binding in soils Soil improvement (reduced use of herbicides/pesticides, water, less soil erosion, higher crop yield, aesthetics,…) 4 October 2024 DTU Sustain Composting in DK  Lifecycle inventory (LCI) for central composting Mass input and mass output (MFA) Composition of input and output SFA) Quantified gas emissions User survey to determine substitution of fertilizer and peat in private gardens Collection scheme of private persons picking up compost at the facility 4 October 2024 DTU Sustain Composting in DK  LCI (Aarhus) central composting LCI data Amount Unit Inputs Waste Amount of garden waste 16,220 Mg ww yr-1 Energy Electricity 0.2 kWh Mg-1 ww consumption Diesel 3.04 L Mg-1 ww Materials Lubricating grease 0.013 L Mg-1 ww consumption Motor oil 0.005 L Mg-1 ww Hydraulic oil 0.005 L Mg-1 ww Cleaning fluid 0.001 L Mg-1 ww Outputs Gaseous emissions CO2-C biogenic 86 ± 10 kg Mg-1 ww (to atmosphere) 97.6 (% of total C emitted) CH4-C 1.9 ± 0.4 kg Mg-1 ww 2.1 (% of total C emitted) N2O-N 0.05 ± 0.01 kg Mg-1 ww 23 (% of total N emitted) CO-C 0.12 ± 0.06 kg Mg-1 ww 0.3 (% of total C emitted) Liquid emissions Leachate L Mg-1 ww 0 (to groundwater) Products Compost 649 kg Mg-1 ww (and rejects) Wood to incineration kg Mg-1 ww 37 (screen rejects) Wood to incineration kg Mg-1 ww 31 (sorting rejects) Hard materials to kg Mg-1 ww 4.8 C&D facility Foreign items to incineration kg Mg-1 ww 6.5 4 October 2024 DTU Sustain Composting in DK  Lifecycle assessment (LCA) in Aarhus (non-toxic categories) The composting facility is the most contributing process to positive PE Use of compost is the main contributor to negative PE 4 October 2024 DTU Sustain Composting in DK  LCA in Aarhus net benefits The environmental profile can be improved by: – Incineration of parts of the garden waste (2-4) – Home composting of part of the garden waste (5-6) 4 October 2024 DTU Sustain Composting in DK  LCI for home composting Mass input and mass output (full MFA) Composition of input and output Quantified gas emissions 4 October 2024 DTU Sustain Composting in DK  LCA of home composting Environmental impacts from home composting (exemplified by Unit 1) GHG emissions and use of compost most important parameters 4 October 2024 DTU Sustain Composting in DK  LCA of home composting Home composting is performing as good as or better than incineration and landfilling in many impact categories Two exceptions are GW and HT Ambiguous results  no clear best solution for treatment of OHW – Home composting can be promoted 4 October 2024 DTU Sustain Composting in DK  LCA of central and home composting Composting generally has small environmental impact Central and home composting had impacts in the same order: – -6 to 100 mPE tonne-1 ww central composting of garden waste – -2 to 28 mPE tonne-1 ww for toxic categories for home composting of OHW GHG emissions and use of compost is the most important processes in respect to environmental impacts Incineration of parts of the garden waste can be beneficial environmentally speaking (especially in terms of GW) 4 October 2024 DTU Sustain Composting in DK Conclusion 4 October 2024 DTU Sustain Composting in DK  Conclusions and recommendations I GHG can not be avoided from composting of organic waste – But can be minimised Small-scale methods underestimated the emissions and were found to be inappropriate for quantifying GHG from windrow composting of garden waste GHG emissions in the order of 16-111 kg CO2-eq. tonne-1 ww from windrow composting of garden waste GHG emissions in the order of 100-239 kg CO2-eq. tonne-1 ww from home composting of organic household waste – Highest emissions from most frequently mixed composting units Most important environmental processes were identified as the GHG emissions (load) and the potential substitution of peat and fertiliser (saving) 4 October 2024 DTU Sustain Composting in DK  Conclusions and recommendations II Garden waste can be incinerated with energy recovery (electricity and heat) – BUT, only parts of the most woody material Use of compost should be optimised so it is actually used as a substitute for peat and/or fertiliser Home composting can be promoted as a supplementary treatment technology There are a range of processes that can not be assessed in LCA at the moment  we need more method development In general, small impacts from composting of organic waste  large potential for increasing the environmental profile 4 October 2024 DTU Sustain Composting in DK  References I Andersen, J.K., Boldrin, A., Christensen, T.H., Scheutz, C. 2010. Greenhouse Gas emissions from home composting of organic household Waste. Waste Management 30, 2475-2482. Andersen, J.K., Christensen, T.H., Scheutz, C. 2010. Substitution of peat, fertiliser, and manure with compost in hobby gardening: User surveys and cases. Waste Management 30, 2483-2489. Andersen, J.K., Boldrin, A., Christensen, T.H., Scheutz, C., 2010. Mass balances and life- cycle inventory of home composting of organic household waste. Waste Management. In press. Andersen, J.K., Boldrin, A., Christensen, T.H., Scheutz, C., 2010. Home composting as an alternative treatment option for organic household waste: an environmental comparison using life cycle assessment-modelling. Waste Management. In press. Andersen, J.K., Boldrin, A., Samuelsson, J., Christensen, T.H., and Scheutz, C. 2010. Quantification of GHG emissions from windrow composting of garden waste. Journal of Environmental Quality. 39, 713–724. 4 October 2024 DTU Sustain Composting in DK  References II Andersen, J.K., Boldrin, A., Christensen, T.H., Scheutz, C. 2009. Mass balances and life cycle inventory for a garden waste windrow composting plant (Aarhus, Denmark). Waste Management & Research. 28, 1010-1020. Scheutz, C., Samuelsson, J., Fredenslund, A. M., Kjeldsen, P., 2011. Methane emission quantification from landfills using a double tracer approach. Waste Management. 31, 1009-1017. Andersen, J.K., Boldrin, A., Samuelsson, J., Christensen, T.H., Scheutz, C., 2010. Quantification of GHG emissions from windrow composting of garden waste. Journal of Environmental Quality 39, 713–724. Galle, B., Samuelsson, J., Svensson, B.H., Börjesson, G., 2001. Measurements of methane emissions from landfills using a time correlation tracer method based on FTIR absorption spectroscopy. Environmental Science & Technology 35 (1), 21-25. 4 October 2024 DTU Sustain Composting in DK  Emissions are NOT measured but calculated Direct GHG emissions from the waste in DK Current emissions Historical and current emissions *emission factor from IPCC to comply Goal: 67% reduction by 2030 in comparison to 1990 4 October 2024 DTU Sustain Composting in DK  New composting projects The amounts of GW and amounts of compost generated Operation of facilities Use of compost Emissions of CH4 and N2O from composting plants Potential to reduce emissions by changing the operation Test with optimal composting treatment Emissions from soil application of compost products (incl. fresh and raw compost) Environment assessment o Composting o Direct application of shredded GW o Increased incineration o Pyrolysis 4 October 2024 DTU Sustain Composting in DK