2006 年 2 巻 4 号 p. 355-362
In this report, results of life cycle inventory analysis are described for evaluating the environmental impact in food production processes including beer production and tofu production in terms of the cumulative CO2 emission unit. It may be considered that the food production is a process where biomass raw materials are converted into food products which are further packaged in suitable sizes for transportation and sale, by supplying utilities such as electricity, water, fuel, package materials etc. It should be noted that biomass wastes themselves are endowed with carbon-neutral nature and the conversion of food wastes does not leads to any artificial increase of CO2 in the environment except for that due to utility inputs. In order to minimize the environmental impacts from the overall production processes, it is necessary to evaluate the cumulative CO2 emission unit or amount of CO2 emission for every unit processes included in the whole production process and to find the possibility of reducing the CO2 emission for some specific process unit from which a particularly large emission fraction to the whole emission would occur, by selecting an alternative production scheme. Also it may be pointed out that in a food production there are many processes where the material is heated or cooled being accompanied by a large amount of heat input or heat discharge and, therefore, adoption of efficient method(s) for saving energies is important. Furthermore, in the food industries, large amounts of organic solid wastes and wastewater rich in organic dissolved substances are discharged. It is the key issue for decreasing environmental impact from the net food production process how to choose an energy-saving method for treating these wastes. In addition, it is important to exempt from discharging any secondary wastes by producing usable products from the raw food wastes and sub-products. Note that it is an effective way to evaluate the amounts of various wastes in either solid or liquid state on a common elemental-carbon basis. Thus in the present research we evaluate the effect of methane fermentation of solid wastes together with or without liquid waste on the net environmental impact in terms of the cumulative CO2 emission unit by comparing alternative waste treating methods including, incineration, drying, composting and others. It may be important to adopt the most effective way to reduce the environmental impact in treating the food wastes. We should know about two issues regulating the food wastes emission: “Law of Food Waste Recycling” (2001) and “Biomass Nippon Total Strategy” (2002). In these issues, recycling methods for the food wastes are classified into the three methods: (1) utilization as raw materials for fertilizer and feeds, (2) renewal use of food waste as feed, fertilizer, oil, plastics, methane etc., (3) reduction of food wastes including dewatering, drying, fermentation, carbonization etc. The effective utilization of food waste is expected to restrain the global warming, to contribute in leading to the resource-recycling society, to grow the strategic biomass industries and to activate the local economy for agriculture, forestry and fisheries. It should be pointed out that important thing is to minimize the environmental impact on the basis of a LC-CO2 inventory analysis by selecting the best promising way among alternative processes.
