Environmental assessment of CCHP (combined cooling heating and power) systems based on biomass combustion in comparison to conventional generation

Biomass CCHP (combined cooling heating and power) systems based on biomass combustion have already demonstrated their benefits in some operating conditions. However, their environmental and energy performance might not always be better than that of conventional stand-alone generation systems. In order to assess the possible benefits, these plants are evaluated by means of Life Cycle Assessment (LCA) methodology to provide some guidelines regarding their environmental feasibility. A thermodynamic model, which considers the integration of different sizes of cogeneration and cooling units, was developed to contribute to properly defining the life cycle inventory stage. Moreover, the model outputs were used to develop a primary energy savings ratio (PESR) analysis and compare its results with those of the LCA. The LCA results show that, whereas small plant cooling-to-heating ratios cause CCHP plants based on biomass combustion to be environmentally feasible (they imply environmental benefits compared to conventional average stand-alone generation), high plant cooling-to-heating ratios in fact cause them to be environmentally unfeasible. Results also allow us to state that the use of the PESR by itself might not be adequate to assess the steady-state performance of this type of plant because, in some circumstances, it might limit the plant's feasibility when environmental benefits could still be achieved. ► LCA of biomass CCHP systems based on prime movers and chillers integration. ► High C values cause bio-fuelled CCHP plants to be environmentally unfeasible. ► PESR alone might be inadequate to draw conclusions about the plant feasibility.