Energy from forest residues in Turkey: An environmental and economic life cycle assessment of different technologies

Forest residues, as cheap and abundant feedstock, can replace current fossil-energy sources, helping to reduce greenhouse gas (GHG) emissions and improve energy security. Given 27 % of total lands covered with forests, Turkey has a remarkable potential of forest residues from harvesting and industrial activities. This paper thus focuses on evaluating the life cycle environmental and economic sustainability of heat and electricity generation utilising forest residues in Turkey. Two types of forest residues (wood chips and wood pellets) and three energy conversion options are considered: direct combustion (heat only, electricity only and cogenerated heat and power (CHP)), gasification (for CHP) and co-firing with lignite. Results suggest that direct combustion of wood chips for cogeneration of heat and power has the lowest environmental impacts and levelised costs for both functional units (per MWh heat and per MWh electricity generation) considered. Compared to fossil-fuel sources, energy from forest residues has a potential to reduce the climate change impact as well as fossil-fuel, water and ozone depletion by >80 %. However, it also causes an increase in some other impacts, such as terrestrial ecotoxicity. The bioenergy plants have also lower levelised costs than electricity from the grid (except those using wood pellets and gasification regardless of the feedstock) and heat from natural gas. Electricity-only plants using wood chips achieve the lowest LCC, generating net profits. All biomass plants, except the pellet boiler, pay back in their lifetime; however, the economic feasibility of electricity-only and CHP plants is highly sensitive to subsidies for bioelectricity and efficient use of heat. Utilising the currently available forest residues in Turkey (5.7 Mt/yr) for energy provision could potentially reduce the national GHG emissions by 7.3 Mt/yr (1.5 %) and save $0.5 bn/yr (5 %) in avoided fossil-fuel import costs.