If compost born CO2 could be applied in production processes instead of fossil derived carbon dioxide, a net reduction of the GHG balance would be possible. As was mentioned a total of about 150 kg CO2 is emitted per ton of compost raw material. Thus in a facility with a capacity of 100,000 t annually, about 15,000 t of carbon dioxide are produced. In Germany CO2 from composting totals about one Mio t of carbon dioxide, which could be used instead of fossil derived CO2 in industrial or related processes.
A sensible use of compost born carbon dioxide is its application in greenhouses where crops are fertilized by CO2 which improves the yields by about 30-40 percent through a CO2 input of 100 t per hectare annually. Conventionally CO2 is from gas burners or is industrially produced. If compost CO2 was used by a medium sized composting facility, an area of about 150 hectares could be fully supplied. As another advantage the residues from the greenhouse crop can be applied as raw material in the composting process. Moreover, renewable heat energy, produced by the composting process supports climatization of the greenhouse, hence avoiding climate gas emissions from fossil fuels (Soyez, 1990b). It is another advantage of such a combination that excess heat from the greenhouse could be used to support the composting process start, hence reducing energy needs.
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