Читать книгу Encyclopedia of Renewable Energy - James Speight G., James G. Speight - Страница 166

A bioenergy system is an energy system which is comprised of a source which generates energy and modulates it in some manner such that it conveys energy. There is also a mechanism connecting the bioenergy source to a transfer medium and a transfer medium through which the bioenergy flows. There is a coupling mechanism connecting the transfer medium bioenergy sink and a terminal sink which includes a mechanism for the storage and use of the energy. The input and output coupling depend on properties of the source and the transfer medium, likewise for the sink.

To evaluate the performance of a bioenergy system, the entire chain from biomass production up to the end-use should be considered. A major criterion for comparing total bioenergy systems is the net energy yield per hectare. If this net yield is low, the amount of land needed for the net production of a certain amount of energy is high and vice versa. Since land is a scarce commodity, high net energy yields per hectare are favored. Also, the environmental impacts of a specific energy crop are a criterion for selection. Logically, another major criterion is the cost of the biomass per GJ produced (or per GJ of fossil energy replaced).

Biomass for energy conversion is usually considered as a local resource. With appropriate logistic systems, access to biomass can be improved over a large geographical area. In this study, life cycle inventory has been used as a method to investigate the environmental load of selected bioenergy transport chains. As a case study, chains starting in Sweden and ending in Holland have been investigated. Biomass originates from tree sections or forest residues, the latter upgraded to bales or pellets. The study is concentrated on production of electricity; hot cooling water is considered as a loss.

See also: Bioenergy, Bioenergy Crops, Biomass.