polylactate (PLA), which is currently the most common biomass plastic, it is believed that the $ CO_{2} $ emissions in the lifecycle can be reduced by approximately 40%. Use of plastic materials for automobiles currently makes up approximately 10% of a car's weight, and supposing that all of that were

and disposed of within a time period shorter than the petroleum-derived plastic, it may not necessarily lead to a reduction of the environmental load. Therefore, when using biomass plastic it is important to keep recycling and other forms of cyclical use in mind, and we should not produce and dispose of biomass plastic lightheartedly. There are also expectations for the development of technologies and systems that enable effective manufacturing of biomass plastic that uses cellulose from rice straw and timber as its raw materials, so as not to impact the stable supply of food and the use of existing timber.

### C. Promoting Use of Biogas

Efforts are being made to use biogas as an energy source to replace fossil fuels. In order to reduce reliance on fossil fuels and ensure a stable and appropriate supply of energy, in 2009 Japan enacted the “Law for Sophisticated Methods of Energy Supply Structures” and revised the “Law concerning Promotion of the Development and Introduction of Alternative Energy.” In addition, in the Basic Energy Plan (decided upon by the Cabinet in June 2010) the government stipulated policies for expanding use of biomass through cooperation by the government and the private sectors. Many such efforts are being made to expand the use of biomass.

One of those efforts is the recovery of energy from sewage sludge and food residue. One of such actions currently in progress involves refining methane gas from the biogas generated by sewage treatment facilities and food factories and using in the same way as city gas (Figure 4-3-18). Specifically, biogas is used on the site of production, used as raw material at city gas plants, and injected into the gas grid pipes. Biogas is mainly replaced with materials made from plants, approximately $ 200 \, kg-CO_{2}e $ could be reduced per vehicle. Assuming simply that biomass plastic was used in the entire world's annually produced 70 million cars, we can reduce approximately 14 million $ CO_{2}e $ annually.

Figure 4-3-18 Phases of Biogas Utilization

used on the site of production, but in recent years several pilot projects have been launched in Tokyo and the City of Kobe to verify the supply of biogas through injection into the gas grid. Through these projects a total of approximately 4,000 ordinary residences, in Tokyo and the City of Kobe, are being supplied with volumes of gas to be used for a year, and it is hoped that 2,560 tons of carbon dioxide will be reduced annually.

Large quantities of sewage sludge are potentially available as resources, and the sewage sludge in Japan is expected to have a potential of approximately 1 million kl of crude oil equivalent. However, only about 10% of sewage sludge is being utilized. At present, there are projects to utilize the unused sewage sludge as energy, and in order to expand use of biogas, the government is setting targets for General Gas Utilities to use at least 80% of the estimated volume (that is, the volume that can be procured at an appropriate cost) of surplus biogas generated by sewage treatment facilities in 2015.