WILLOW FIRING IN RETROFITTED IRISH PEAT POWER-PLANTS

Concerns about CO2 emissions have caused renewed interest in biomass e lectricity in Ireland. A low-investment-cost option is the firing of l ocally grown willow in retrofitted Irish peat plants. Various options for such a biomass energy system were evaluated. All steps in the supp ly chain were integrated in a model and optimised economically. Retrof itting of existing peat plant was compared with building new biomass c ombustion and gasification plants. All conversion technologies conside red are able to co-fire biomass and peat. The study focused on possibi lities in the short term. To reflect uncertainties, all costs were pre sented in ranges. Neither agricultural subsidies nor possible CO2 taxe s were included. The lowest cost retrofit option with a proven technol ogy was the conversion of unit 3 of the Lanesborough peat plant into a bubbling fluidised bed. The willow costs at the plant gate ranged bet ween 4.4 and $15/GJ(LHV) and the kW h costs between 7.5 and 21 cent/kW h. The not yet proven options of gasification and the retrofit into a whole-tree energy plant showed slightly lower costs. The large ranges in the costs were mainly caused by the difference between the low and high estimation of the willow yields and the farmer's annual income. It can be concluded that in the lowest cost estimate, willow firing in retrofitted Irish peat plants has about the same cost as peat firing. ($4.3/GJ(LHV) and 7.4 cent/kW h) and could therefore be a promising o ption to reduce CO2 emissions in Ireland. (C) 1997 Elsevier Science Lt d.