Environmental Impacts of Recycling of Waste Plastics in Yokohama City

Abstract

Yokohama City started to collect and recycle waste plastic containers and packaging from all households (about 1.5 million households) in April 2005. At present, the collected waste plastics are chemically recycled into reducing agents for blast furnace and ammonia, although they had been burned together with other household wastes in the past. The present study evaluates environmental impacts of recycling the waste plastics instead of incineration in Yokohama City. This study found that waste plastics recycling greatly decreases the overall emissions of carbon dioxide (CO₂) and solid waste as compared with the incineration case. While the recycling increases emissions from additional recycling-related processes, it decreases the emissions from the normal processes of coke and ammonia production. The former increase is almost the same as, or a little more than, the latter decrease. However, since the emissions from incineration factories of the city in the recycling case are much less than those in the incineration case, the recycling can reduce the overall CO₂ and solid waste emissions considerably. In contrast, the overall emissions of sulfur oxides and nitrogen oxides in the recycling case were evaluated to be higher than those in the incineration case. The city has superior waste incineration factories, from which the emissions caused by incineration of waste plastics are extremely low. Thus, even if the waste plastics are recycled instead of incineration, the emissions from their incineration factories change only little. On the other hand, the emissions from recycling and power generation processes increase in the recycling case. As a result, the recycling does not reduce the overall emissions of sulfur oxides and nitrogen oxides.