Food Waste Streams Research Articles

An analysis of a community food waste stream

Food waste comprises a significant portion of the waste stream in industrialized countries, contributing to ecological damages and nutritional losses. Guided by a systems approach, this study quantified food waste in one U.S. County in 1998–1999. Publications and personal interviews were used to quantify waste from food production, processing, distribution, and consumption. Approximately 10,205 tons of food waste was generated annually in this community food system. Of all food waste, production waste comprised 20%, processing 1%, distribution 19%, and 60% of food waste was generated by consumers. Less than one-third (28%) of total food waste was recovered via composting (25%) and food donations (3%), and over 7,000 tons (72%) were landfilled. More than 8.8 billion kilocalories of food were wasted, enough to feed county residents for 1.5 months. This case study offers an example of procedures to quantify and compare food waste across a whole community food system.

Parameter Estimation for Simultaneous Saccharification and Fermentation of Food Waste Into Ethanol Using Matlab Simulink

The increase in waste disposal and energy costs has provided an incentive to convert carbohydrate-rich food waste streams into fuel. For example, dining halls and restaurants discard foods that require tipping fees for removal. An effective use of food waste may be the enzymatic hydrolysis of the waste to simple sugars and fermentation of the sugars to ethanol. As these wastes have complex compositions which may change day-to-day, experiments were carried out to test fermentability of two different types of food waste at 27 degrees C using Saccharomyces cerevisiae yeast (ATCC4124) and Genencor's STARGEN enzyme in batch simultaneous saccharification and fermentation (SSF) experiments. A mathematical model of SSF based on experimentally matched rate equations for enzyme hydrolysis and yeast fermentation was developed in Matlab Simulink. Using Simulink parameter estimation 1.1.3, parameters for hydrolysis and fermentation were estimated through modified Michaelis-Menten and Monod-type equations with the aim of predicting changes in the levels of ethanol and glycerol from different initial concentrations of glucose, fructose, maltose, and starch. The model predictions and experimental observations agree reasonably well for the two food waste streams and a third validation dataset. The approach of using Simulink as a dynamic visual model for SSF represents a simple method which can be applied to a variety of biological pathways and may be very useful for systems approaches in metabolic engineering in the future.

Metal ion separation and protein removal from aqueous solutions using modified cellulose acetate membranes: Role of polymeric additives

Metal ion separation from industrial effluents and protein removal from food and bio-related industrial waste streams are gaining increased visibility due to environmental concern and saving valuable materials. In this work, an attempt has been made to remove the valuable proteins and metal ions using modified cellulose acetate (CA) based membranes prepared in the absence and presence of the polymeric additives such as polyvinylpyrrolidone (PVP) and polyethyleneglycol (PEG 600) in various compositions. Studies were carried out to find the rejection and permeate flux of proteins such as bovine serum albumin (BSA), pepsin and trypsin and metal ions such as Cu(II), Zn(II), Co(II), and Cd(II) using polyethyleneimine (PEI) as the chelating ligand. On increasing concentrations of PVP and PEG, the rejection of proteins and metal ions is decreasing while the permeate flux has an increasing trend. These effects are due to the increased pore formation in the CA membranes because of the additives. In general, it was found that CA/PVP blend membranes displayed higher permeate flux and lower rejection compared to CA/PEG blend membranes at all additive concentrations. The extent of separation of proteins was found to be directly proportional to the molecular weight of the protein while the extent of removal of metal ions depends on the affinity of metal ions to PEI to form macromolecular complexes and the stability of the formed complexes.

SE—Structures and Environment: A Dual-reactor Anaerobic System for Complete Treatment of a Food Processing Waste

Anaerobic technologies are commonly employed for the initial treatment of food processing wastewater; however, they are not typically considered capable of treating wastewater to meet final discharge requirements. To assess the potential of anaerobic technologies to meet discharge requirements, the performance of two dual-reactor high-rate anaerobic systems fed with confectionery wastewater was investigated. The primary reactors in the system were operated at constant hydraulic retention times of 1·6 d. The secondary reactors were operated with hydraulic retention times of 0·8, 1·6, and 3·2 d. The secondary reactors, which were both downflow anaerobic filters, achieved maximum chemical oxygen demand (COD) removal rates when operated at a hydraulic retention time of 1·6 d. The brick-filled downflow anaerobic filter and the plastic-ring-filled downflow anaerobic filter produced average effluent five-day biochemical oxygen demand concentrations of 26 mgl−1 (COD=80 mg l−1) and 36 mg l−(COD=112 mg l−1), respectively. To examine the enhanced stability provided by the sequential reactor approach, the dual-reactor system was overloaded at 3·5 times the normal COD concentration (8000 mg l−1) for an 8 h period. The secondary reactors were able to accommodate the increased organic loading emitted from the primary reactors, maintaining an overall removal efficiency of >994%. The results suggest that full anaerobic treatment of readily degradable food waste streams may be realistic, and that a sequential reactor approach significantly enhances overall process stability.

Life Cycle of Silicone Polymer, from Pilot-Scale Composting to Soil Amendment

Silicone polymers (polydimethylsiloxanes, or PDMS) are used in numerous down-the-drain products which can eventually enter wastewater treatment plants, where they become incorporated into the sludge. Since sludge is sometimes composted before being applied to the land, this work investigates the fate of PDMS from its incorporation into sludge, through pilot-scale composting processes, to its degradation in compost-amended soil.Either yard or food waste streams were composted in 60 liter vessels with sludge which contained either no PDMS, or had been amended with 350 cs PDMS at 2000 mg/kg wet weight sludge. The four treatments (yard waste and food waste, no PDMS; yard waste and food waste with PDMS) were composted for six weeks and showed expected profiles of temperature, O2, and CO2 changes as the composts matured. Mature composts (pH of 8.4, ash content of 46%, degree of humification of 90%, and C:N ratio of 12) were extracted and showed no degradation of the PDMS during compost generation. Cress seeds (Lepidium sativum) were germinated and grown for two days in the presence of water extracts of the finished composts; results indicated no trends in phytotoxicity between the composts with and without PDMS.PDMS degraded when samples were submitted to weekly or twice-weekly wetting/drying cycles in the laboratory. Degradation in compost or compost/soil samples (15 to 20% in one month) compared to >80% for neat PDMS spiked into soil indicates that PDMS may need to move off the compost and onto the soil minerals for more rapid degradation to occur. PDMS degradation was confirmed in compost/soil mixes under field conditions: ~60% degraded during the 1998 growing season. In general, results show that PDMS will proceed inertly through the active composting process, and will then degrade both during outside storage of compost, and after compost is mixed with soil.

Closed system for local reuse of blackwater and food waste, integrated with agriculture

To increase the recycling rate of blackwater and food waste to farm land, a small scale system, independent of sewer pipelines and sewage works, has been developed. It reduces water and air pollution, allows for source control of the recycled material, integrates farmers into the waste handling business, and reduces domestic water consumption. Parts of the system have been implemented in four Norwegian communities. Greywater is treated in local nature-based systems or in a new compact filter unit. Food waste and blackwater from new water saving toilets is stored in sub-surface tanks close to the house for one to two years, and then treated in a closed system. By combining the separate blackwater and food waste streams into one, logistics are greatly simplified. After collection by a tanker, the material is sanitised and stabilised in a thermophilic aerobic reactor, especially suited for decentralised solutions. No ammonia is lost, and the product has the highest possible agronomic value, with respect to nutrient content and organic matter. The treated material is spread onto farm land during the growing season. The different parts of the system can be implemented step by step over a longer time period.

Closed system for local reuse of blackwater and food waste, integrated with agriculture

To increase the recycling rate of blackwater and food waste to farm land, a small scale system, independent of sewer pipelines and sewage works, has been developed. It reduces water and air pollution, allows for source control of the recycled material, integrates farmers into the waste handling business, and reduces domestic water consumption. Parts of the system have been implemented in four Norwegian communities. Greywater is treated in local nature-based systems or in a new compact filter unit. Food waste and blackwater from new water saving toilets is stored in sub-surface tanks close to the house for one to two years, and then treated in a closed system. By combining the separate blackwater and food waste streams into one, logistics are greatly simplified. After collection by a tanker, the material is sanitised and stabilised in a thermophilic aerobic reactor, especially suited for decentralised solutions. No ammonia is lost, and the product has the highest possible agronomic value, with respect to nutrient content and organic matter. The treated material is spread onto farm land during the growing season. The different parts of the system can be implemented step by step over a longer time period.

Computer optimization of reverse osmosis processing of soy whey with cellulose acetate modules

AbstractIn processing full‐fat soy flour to an acid‐precipitated lipid protein concentrate a byproduct whey fraction results which, because of its high biological oxygen demand, represents a serious disposal problem. Processing of food waste streams by reverse osmosis has received considerable attention because of its low theoretical energy requirement since no phase change is involved. In a previous study at this Center a mathematical model was developed for the diffusive transport of soy lipid protein concentrate whey across cellulose acetate membranes. In this study, pumping energy and power costs combined with membrane life and replacement costs were incorporated into the original model to provide a basis for optimization from an energy cost standpoint. Computer‐simulated runs were compared with experimental pilot‐plant runs, and the agreement between predicted and actual results was quite good. Water flux rates were in the range of 3 to 7 gal/ft2/day. Computer runs were used to optimize the processing of 100,000 gal/day of soy whey at 8000 ppm biological oxygen demand (BOD). Costs were at a minimum with a six‐stage tapered flow primary reverse osmosis treatment over a porous cellulose acetate membrane, followed by a six‐stage tapered flow reverse osmosis over a tighter membrane. BOD reduction was 94% at a cost of $5.45/1000 gal.

Water and solute transport across cellulose acetate membranes in the treatment of soybean whey by reverse osmosis

AbstractIn processing full‐fat soy flour to produce an acid‐precipitated lipid protein concentrate, there results a by‐product whey fraction which, because of its high biological oxygen demand, represents a serious disposal problem. Processing of food waste streams by reverse osmosis has received considerable attention because of its low theoretical energy requirement, since no phase change is involved. A series of statistically designed and analyzed experiments were conducted on a pilot‐plant reverse osmosis unit to study the effect of the operating parameters on solute and solvent transport in cellulose acetate membranes. Sucrose and sodium chloride solutions were tested in addition to soybean whey to relate the mixed solute system in whey to that of single‐solute organic and inorganic feed solutions. Water flux was shown to have an Arrhenius dependency on temperature, and some membrane compaction was observed with the more porous membrane. Concentration polarization for sucrose and sodium chloride solutions increased linearly with water flux. Solute flux for soybean whey solutions decreased with molarity and was independent of pressure, whereas solute rejection increased with temperature and pressure and was independent of molarity. Good agreement was obtained using the derived parameters A, B, and τ for soy whey in the diffusion transport model when compared to the observed experimental values.