Abstract

This analysis describes the handling of biodegradable park and garden waste in the municipality of Lund in Sweden, from these three different perspectives: impact on environment, energy consumption and costs. Today‘s methods, as well as some other different possibilities in recycling of park and garden waste are investigated. A limitation in the analysis is that all the park and garden waste handled in the municipality is either composted or returned directly to the area after shredding. Composting may be carried out either regionally at SYSAV's "mattress" compost plant (see fig. 2) at Spillepeng in Malmö, or locally on a smaller scale in the municipality of Lund. These limitations allow the impact on the environment to be equal to the fuel consumption for transports and treatment of park and garden waste. More than 7000 tonnes of park and garden waste are produced in the municipality of Lund every year. Almost half of this comes from the household‘s garden waste. The remainder originates from different housing companies, church-yard management, parks etc. Almost half of the park and garden waste from the municipality of Lund is transported to the regional "mattress" compost at Spillepeng. The rest is treated at local windrow composting plants, by home composting or by composting in different areas e.g. in residential areas and in allotments, and by bringing it back, after shredding, to where it originated. Transporting park and garden waste is both energy consuming and expensive, since the material is voluminous. By shredding the park and garden waste it is possible to increase volume weight by four to six times. With the higher volume weight the efficiency of the transports will increase as well. While the distance of transport exceeds 25 km, the handling of park and garden waste will not be as costly and energy consuming if it is shredded before the transport to a mattress compost plant, as when it is transported unshredded. The cost and energy consumption for the shredding are covered by the higher efficiency in transport, at this distance. Most of the larger composting plants for park and garden waste in Sweden are big central windrow composts. There are small differences in costs and energy consumption between different sizes of windrow composts. This means that long transports of park and garden waste to large central windrow compost plants, compared to short transports to small windrow compost plants, is not a way to save costs and energy. Composting at "mattress" compost plants is not as costly and energy consuming as composting in windrow compost plants. On the other hand, to make a "mattress" compost plant profitable, there must be more than 5000 tonnes of park and garden waste composted every year. If the park and garden waste is shredded at a recycling station it may also be possible to compost it in windrows at the station. Costs and energy consumption for composting park and garden waste are higher at local windrow composts than at regional "mattress" composts. The costly and energy consuming transports of park and garden waste, on the other hand, makes the handling less energy consuming and costly if the park and garden waste is composted locally at a windrow compost, compared to transporting it to a regional mattress compost, if the transport distance exceeds 5-6 km. If` all park and garden waste from the municipality of Lund is transported to the regional "mattress" compost plant at Spillepeng, the cost and fuel consumption are calculated to be approx. SEK 5.l millions and approx. 125 m3 diesel/year respectively. If all the park and garden waste is handled within the municipality by home composting of garden waste and by shredding all the park waste before transport to a local windrow compost, the cost is calculated to decrease to less than SEK 3 millions and the fuel consumption is calculated to decrease to about 20 m3 diesel/year. Composting is not an end in itself, but it is a way to recycle park and garden waste from green urban areas. By bringing the biodegradable organic material back directly after shredding it, it is also possible to recycle park and garden waste. Another way of recycling is burning ligneous material and digesting biodegradable material with a high amount of nitrogen, followed by spreading of ash and digestion rests. To evaluate the impact on the environment and costs for these alternatives further research is needed. To clarify differences in emissions and the impact on the environment of different processes of decomposition of park and garden waste such as "matress" composting, windrow composting, home composting, natural decomposition, digesting and burning, thorough measurements of emissions from these processes are needed.

Keywords

organiska restprodukter

Published in

Rapport - Sveriges lantbruksuniversitet, Institutionen för lantbruksteknik
1996,
Publisher: Institutionen för lantbruksteknik, Sveriges lantbruksuniversitet

Permanent link to this page (URI)

https://res.slu.se/id/publ/125816