Solid waste composting and the application of compost for biosurfactant production

In Canada, about 9 million tonnes of residential waste with over 40% of organic waste was disposed every year. Another major source of organic waste in Canada is from the seafood processing industry. For effective organic waste management, composting serves as a sound, cost-efficient and environmental friendly measure. The selection of bulking agents is of primary importance to adjust the moisture and carbon/nitrogen (C/N) ratio of organic waste during composting. Therefore, initially, the performance of locally available bulking agents (i.e., sawdust and peat in Newfoundland and Labrador (NL)) during organic municipal solid waste (MSW) composting was evaluated. Results indicated that to generate a high temperature and a longer duration of high temperature to kill pathogens and sterilize the compost, peat was considerably more effective. A design of experiment (DOE) based methodology was then adopted to investigate the effects of multiple factors including C/N ratio, moisture content (MC), type of bulking agent (BA) and aeration rate (AR) and their interactions on the maturity, stability and toxicity of compost product. For the first time, enzyme activities were used as indices of maturity and stability during the course of a DOE based composting. The results provided guidance to optimize a MSW composting system that will lead to increased decomposition rate and the production of more stable and mature compost. Thirdly, the feasibility of using enzyme activities for indicating the state of marine fish waste composting was also examined. A good correlation among enzyme activities and different physiochemical parameters including oxygen uptake rate (OUR), C/N ratio, and germination index (GI) led to the conclusion that enzyme activities could be feasible indicators of the state and evolution of the composting process. Raw materials contribute about 30% of the biosurfactant production cost. Evaluation of the feasibility of using fish waste compost (FWC) extract as an unconventional substrate for biosurfactant production was highly desirable to refine the utilization of FWC and achieve the economical biosurfactant production. In this study, the nutrient extraction from FWC was achieved by enzyme hydrolysis and optimized using response surface methodology (RSM). The extract was used to produce biosurfactants by Rhodococcus erythropolis sp. P6-4P and bacillus sp. N3-1P strains. FWC extract showed a good potential as an unconventional source of nutrient for microbial growth. The obtained biosurfactants showed excellent properties with high surface tension reduction, high emulsification activity, and exhibited a high level of stability. The research outputs can contribute to the technical and scientific knowledge to design and operate composting system to manage the organic MSW and fish waste by achieving a double benefit of waste reduction while producing marketable products. Additionally, the products and the bioprocess can be of great value to both scientific understanding and industrial applications

ENV-653: PRODUCTION OF BIOSURFACTANT BY RHODOCOCCUS ERYTHROPOLIS SP. CULTIVATED IN A NOVEL FISH WASTE COMPOST EXTRACT SUBSTRATE

Compost generated through fish waste composting could provide an effective source of nutrient-rich organic matter for microbial growth, leading to the production of valuable products such as biosurfactants. Existing biosurfactant production is a relative expensive process and raw materials contribute about 30% of the production cost. Utilizing waste streams such as fish waste compost (FWC) as a substrate is an economically viable alternative. In this study, biosurfactant was produced by Rhodococcus erythropolis sp. P6-4P, a strain isolated from the North Atlantic Ocean. Biosurfactant production with FWC extract was compared with other soluble and insoluble carbon and nitrogen sources using emulsification assay and surface tension measurement. FWC extract showed good potential as an unconventional source of nutrient for microbial growth. The produced biosurfactant under optimum condition obtained via response surface methodology was further characterized for total carbohydrate, total lipid and total protein content. The results provided evidence for using FWC extract as a novel substrate for biosurfactant production

Composting of Municipal Sludge - Riverhead Wastewater Treatment Facility

A significant amount of biosolids is generated by the Riverhead Wastewater Treatment Facility (RHWTF) every year. Although biosolids have the potential to be transformed into compost through the composting process, the usual practice is to dispose them into landfills. Composting helps stabilize the organic matter in the biosolids (Oleszczuk, 2008), and the heat generated during the thermophilic phase also kills pathogens. The organic content of the sludge will be converted into stabilized humic substances through mineralization and, hence, the volume of the sludge is significantly reduced (Gouxue et al., 2001). These composted biosolids, once applied to the soil, can accelerate plant growth, improve soil moisture retention, increase organic matter in the soil, and control erosion of the topsoil (Liang et al., 2003). Since the RHWTF-generated biosolids have a very low carbon to nitrogen (C/N) ratio (8:1), they are usually landfilled. The fly ash (FA) generated from Corner Brook Pulp and Paper (CBPP), however, has a high carbon content; its addition to biosolids could increase the C/N ratio of biosolids. Therefore, the main objective of this study is to investigate the potential application of locally available carbonenriched ash from CBPP in improving the quality of biosolids generated by RHWTF, which serves the City of St. John’s, Mount Pearl, and Paradise

Development of Advanced Composting Technologies for Municipal Organic Waste Treatment in Small Communities in Newfoundland and Labrador

Municipal Solid Waste (MSW) is one of the major fractions of the solid waste in Canada. From 2002 to 2008, Canadian municipal solid waste disposal has increased from 769 kilograms to 777 kilograms per capita. Among the provinces, Newfoundland and Labrador (NL) has one of the highest waste disposal levels per capita in the country. According to the Multi Materials Stewardship Board (MMSB), it is estimated that more than 400,000 tonnes of municipal solid waste (MSW) materials are generated each year in this province and organic waste makes up as much as 30% of all waste generated. To properly manage MSW generated, the Provincial Solid Waste Management Strategy has been identified in 2002, aiming to reduce the amount of waste going into landfills by 50 per cent. Composting has been regarded as an efficient and effective way to deal with the organic waste and helps work toward achieving the provincial 50 per cent waste reduction goal. It also creates rich organic soil that can enhance lawns and gardens. Therefore, MSW composting has been listed as one of the six new environmental standards applied to new waste management systems in NL. However, NL comprises more than 200 small communities without access to the central composting facility. For those areas, small-scale composting technologies are desired to manage their MSW so as to reduce collection and transport costs and eliminate the other environmental contamination during transportation. Composting is a biological process that is affected by chemical and physical factors. The lack of understanding of the complexity of biological, chemical, and physical processes can result in malfunction of a composting system. The microbial and physicochemical environment in composting can be affected by the diversity of microbial population, temperature, bulking agent, aeration, and chemical properties of raw material such as the C/N ratio and moisture content. Interactions among biological, chemical, and physical factors are crucial to the comprehensive understanding of the composting process, and thus viable for process control and system optimization. This project aims at developing composting technologies applicable to northern communities in NL, and conducting system optimization to increase the composting efficiency and improve compost quality. Six composting reactors (50×20×25 cm) were designed and manufactured. Six mixers were installed in each reactor. An inlet was designed to provide air through a vacuum pump. A perforated plate with holes was installed for air distribution in the system. The exhaust gas was monitored by a gas monitoring system and then discharged into a flask containing H2SO4 solution (1 M) to absorb the NH3. To prevent heat loss, heat insulating layers were designed and applied to cover the reactor thoroughly. Reactors were filled with food waste as raw material. Factorial design was applied, with sixteen runs conducted, to optimize the operational factors including moisture content, aeration, bulking agent, and C/N ratio. Each composting run lasts 30 days. The effect of main factors and their interactions on composting process was investigated by measuring temporal variations of enzyme activities (dehydrogenase, β-glucosidase, and Phosphomonoesterase), germination index (GI), pH, electrical conductivity (EC), temperature, moisture, ash content, oxygen uptake rate (OUR), and C/N ratio during composting. Experimental results showed that the breakdown of organic matter by microbial activities led to increase in the temperature of the composting material. As composting progresses, the amount of degradable matter decreased and the temperature declined. When most of the organic matter was consumed, the temperature in the reactor dropped to the ambient temperature. The OUR can express biological activities during composting and biological stability at the end of composting. The OUR values showed strong correlation with temperature. The maximum OUR was observed concurrently with the maximum temperature. The pH value was low at the first stage due to the accumulation of organic acids, and increased gradually while organic acids were consumed by microorganisms. The EC values increased in all runs as a result of cation concentration increment. Moisture content showed descending trends in all runs due to the evaporation under high temperature. As a result of decomposition of organic matter by composting, the organic matter decreased and ash content increased in all runs. Although the GI data showed notable fluctuation during composting, it started to increase at the end of the composting process. In most of the runs, the peaks of dehydrogenase activity as an indicator of biological activity were observed with the maximum temperature and OUR value simultaneously. The β-glucosidase activity showed with high values at the themophilic phase and after the temperature drop. In addition, high activity of phosphomonoesterase accrued during the thermophilic phase. Results of the factorial design indicated that aeration rate, moisture content, and bulking agents affect the maximum temperature significantly. Aeration rate has significant influence on the maximum OUR. The C/N ratio and the interaction between aeration rate and bulking agent have major impact on GI. Moisture content is an important factor affecting the cumulative dehydrogenase and the β-glucosidase activity. The C/N ratio influences the β-glucosidase activity as well. The output of this research can help to design the small-scale composting system for MSW management in small communities in NL, and provide a solid base of technical and scientific knowledge for system operation

Performance of locally available bulking agents in Newfoundland and Labrador during bench-scale municipal solid waste composting

Background: Newfoundland and Labrador (NL) has one of the highest waste disposal rates in Canada and it has 200 small communities without access to central composting facilities. During Municipal solid waste (MSW) composting, the selection of bulking agents is critical. Bench-scale composting systems plus locally available bulking agents are thus desired for economic and effective MSW management in NL communities. This study evaluated the performance of locally available bulking agents (i.e., NL sawdust and peat) during MSW composting in a bench-scale system. Physiochemical (temperature, oxygen uptake rate, pH, electrical conductivity, moisture and ash content, and C/N ratio) and biological (enzyme activities and germination index) parameters were monitored to evaluate compost maturity and stability. Results: In peat composting, higher temperature for a longer duration was observed, indicating more effective pathogen removal and sterilization. High enzyme activities of dehydrogenase, β-glucosidase, and phosphodiesterase in the third week of composting imply high microbial activity and high decomposition rate. The low C/N ratio for compost product implies acceptable stability states. In sawdust composting, higher temperature and oxygen uptake rate (OUR) were observed in the third week of composting, and higher enzyme activities in the second week. Sawdust composting generated a higher germination index, indicating higher maturity. Conclusions: Both sawdust and peat are effective bulking agents for the bench-scale composting. The choice of a bulking agent for a particular community depends on the availability of the agent and land in the region, convenience of transportation, price, and the expected quality of the compost product