Bijaya K. Adhikari

Effectiveness of three bulking agents for food waste composting.

Rather than landfilling, composting the organic fraction of municipal solid wastes recycles the waste as a safe and nutrient enriched soil amendment, reduces emissions of greenhouse gases and generates less leachate. The objective of this project was to investigate the composting effectiveness of three bulking agents, namely chopped wheat (Triticum) straw, chopped mature hay consisting of 80% timothy (milium) and 20% clover (triphullum) and pine (pinus) wood shavings. These bulking agents were each mixed in duplicates at three different ratios with food waste (FW) and composted for 10 days using prototype in-vessel composters to observe their temperature and pH trends. Then, each mixture was matured in vertical barrels for 56 days to measure their mass loss and final nutrient content and to visually evaluate their level of decomposition. Chopped wheat straw (CWS) and chopped hay (CH) were the only two formulas that reached thermophilic temperatures during the 10 days of active composting when mixed with FW at a wet mass ratio of 8.9 and 8.6:1 (FW:CWS and FW:CH), respectively. After 56 days of maturation, these two formulas were well decomposed with no or very few recognizable substrate particles, and offered a final TN exceeding the original. Wood shavings (WS) produced the least decomposed compost at maturation, with wood particles still visible in the final product, and with a TN lower than the initial. Nevertheless, all bulking agents produced compost with an organic matter, TN, TP and TK content suitable for use as soil amendment.

Predicted growth of world urban food waste and methane production

Landfill gas emissions are one of the largest anthropogenic sources of methane especially because of food waste (FW). To prevent these emissions growing with world population, future FW best management practices need to be evaluated. The objective of this paper was therefore to predict FW production for 2025 if present management practices are maintained, and then, to compare the impact of scenario 1: encouraging people to stay in rural areas and composting 75% of their FW, and; of scenario 2, where in addition to scenario 1, composting or anaerobically digesting 75% of urban FW (UFW). A relationship was established between per capita gross domestic product (GDP) and the population percentage living in urban areas (%UP), as well as production of municipal solid waste (MSW) and UFW. With estimated GDP and population growth per country,%UP and production of MSW and UFW could be predicted for 2025. A relatively accurate (R 2 > 0.85) correlation was found between GDP and%UP, and between GDP and mass of MSW and FW produced. On a global scale, MSW and UFW productions were predicted to increase by 51 and 44%, respectively, from 2005 to 2025. During the same period, and because of its expected economic development, Asia was predicted to experience the largest increase in UFW production, of 278 to 416 Gkg. If present MSW management trends are maintained, landfilled UFW was predicted to increase world CH4 emissions from 34 to 48 Gkg and the landfill share of global anthropogenic emissions from 8 to 10%. In comparison with maintaining present FW management practices, scenario 1 can lower UFW production by 30% and maintain the landfill share of the global anthropogenic emissions at 8%. With scenario 2, the landfill share of global anthropogenic emissions could be further reduced from 8 to 6% and leachate production could be reduced by 40%.

Home and community composting for on-site treatment of urban organic waste: perspective for Europe and Canada.

As a result of urbanization and economic prosperity, which has accelerated the generation of municipal solid waste (MSW) along with its organic fraction, the management of MSW is a challenge faced by urban centres worldwide, including the European Union (EU) and Canada. Within a concept of waste recovery, the source separation and on-site treatment of urban organic waste (UOW) can resolve some of the major economic issues faced by urban centres along with the environmental and social issues associated with landfilling. In this context and in a comparison with the traditional landfilling practice, this paper examines on-site UOW composting strategies using a combination of centralized composting facilities, community composting centres and home composting. This study consisted of a feasibility and economic study based on available data and waste management costs. The results indicate that on-site treatment of UOW using practices such as home and community composting can lower management costs by 50, 37 and 34% for the rich European countries (annual GDP over US

Urban Food Waste generation: challenges and opportunities.

25 000), the poorer European countries (annual GDP under US

Performance of five Montreal West Island home composters

25 000), and Canada, respectively. Furthermore, on-site composting can reduce greenhouse gas emissions by 40% for Europe and Canada, despite gas capture practices on landfill sites. However, the performance of home composters and the quality of the compost products are issues to be further addressed for the successful implementation of UOW on-site composting.

Home composting of organic waste – part 1: effect of home composter design

Greater economic activity and a wider economic gap between rural and urban areas is leading to accelerated urbanisation and the generation of 35% more Urban Food Waste (UFW) from 2007 to 2025. Besides landfilling, this paper examines the advantages of introducing onsite composting and anaerobic digestion for the environmental recycling of UFW and the lowering of handling cost. For Asia and Africa, these solutions for UFW could reduce the mass of MSW by 43% and 55%, respectively, thus help there cities manage almost all of their MSW. For North America and Europe, such practice could reduce earth warming trends.

Home composting of organic waste – part 2: effect of management practices

Even if home composting can eliminate municipal organic waste collection, handling and treatment costs, its compost quality requires investigation outside the laboratory. A study was thus conducted to evaluate the influence of the following management practices on the compost quality produced by five backyards home composters in Montreal West Island from June to October 2010: the type and backyard location of the home composter (HC), and the rate and type of organic waste (OW) fed into the home composter. The parameters monitored were compost temperature and final characteristics including trace elements and pathogens. For all HC compost, maximum but not necessarily thermophilic temperatures were highly probable within one week of adding more than 10 kg of OW composed of equal volumes of food waste (FW) and yard trimmings (YT). Top and bottom HC perforations enhanced convective aeration but concentrated OW decomposition within the bottom layer. Fed an equal volume of FW and YT, the final HC compost had a dry and organic matter content exceeding 30%, and 50%, respectively, and a total nitrogen, phosphorous and potassium level of 2, 1 and 3 % on a dry matter basis, representing a good quality soil amendment. Clean OW feeding resulted in compost respecting Canadian and European regulations for Escherichia coli and Salmonella, irrespective of the temperature regime. For trace elements, regulatory limits may be exceeded when the home composter is fed ashes and soil. Homeowners must also be careful when applying pesticides to their lawns and gardens and then feeding the residues to the home composter.

Production vs. consumption management for sustainable agricultural resources

Worldwide, health and environmental considerations encourage landfill diversion of the organic fraction (OW) of municipal solid wastes, through alternative such as home composting. Of poor sanitation, and trace element and toxic hydrocarbon content (PAH) documentation, this study compared against a laboratory composter (LR), the performance (temperature regime and compost quality) of four 300 to 400 L home composting systems (HC), namely the Plastic (P) and Wood (W) Bins, the Rotary Drum (RD) and the Ground Pile (GP). All were batch loaded with the same food waste (FW) and yard trimmings (YT) mixture for uniform testing. The P and GP performed best in terms of temperature regime, followed by W and LR, while all demonstrated similar dry and organic matter and chemical oxygen demand except for RD with a higher dry matter because of poor aeration. All composts respected regulatory pathogen/parasite counts, trace element and PAH levels.

Characterization of food waste and bulking agents for composting.

Home composting (HC) can produce safe compost if properly managed, while reducing municipal disposal costs. This project investigated the sanitary and safety impact of HC management (with/without bulking agent, batch/weekly feeding, with/without regular mixing) using the Plastic (P) and Wood (W) bins, the Rotary Drum (RD) and the Ground Pile (GP) filled with equal wet volumes of food waste (FW) and yard trimmings (YT). Thermophilic temperatures were obtained only for batch feeding. Mixing the HC compost improved thermophilic temperature duration for W with limited convective aeration, but reduced the duration for P with good convective aeration. Tested only with W and RD, BA reduced the thermophilic period by increasing the compost dry matter from 20% to 40%, lowering the pH from 6.1–7.7 to 5.7, and diluting the biodegradable organic matter. The lowest parasite and pathogen level and odours were obtained in P and GP without BA.

Gas emissions as influenced by home composting system configuration

At 35%, world food production wastage is jeopardising the sustainability of global resources and the future of food security, especially considering that agriculture uses 60% and 37% of the world water and land resources. Ironically, rural populations are most exposed to poverty and hunger when they feed the world. Through a literature review, this paper will demonstrate that supply management, based on consumption, is a solution to food wastage and can in parallel, improve rural wealth, introduce sustainable agricultural practices, resolve major urban pressures and bring about global climate change adaptation. The concepts presented in this paper confront modern world agricultural policies as production management systems are being abolished throughout the world, including Canada.