Life Cycle Assessment of Biomass‐based Combined Heat and Power Plants

Norway, like many countries, has realized the need to extensively plan its renewable energy future sooner rather than later. Combined heat and power (CHP) through gasification of forest residues is one technology that is expected to aid Norway in achieving a desired doubling of bioenergy production by 2020. To assess the environmental impacts to determine the most suitable CHP size, we performed a unit process‐based attributional life cycle assessment (LCA), in which we compared three scales of CHP over ten environmental impact categories—micro (0.1 megawatts electricity [MWe]), small (1 MWe), and medium (50 MWe) scale. The functional units used were 1 megajoule (MJ) of electricity and 1 MJ of district heating delivered to the end user (two functional units), and therefore, the environmental impacts from distribution of electricity and hot water to the consumer were also considered. This study focuses on a regional perspective situated in middle‐Norway's Nord‐ and Sor‐Trondelag counties. Overall, the unit‐based environmental impacts between the scales of CHP were quite mixed and within the same magnitude. The results indicated that energy distribution from CHP plant to end user creates from less than 1% to nearly 90% of the total system impacts, depending on impact category and energy product. Also, an optimal small‐scale CHP plant may be the best environmental option. The CHP systems had a global warming potential ranging from 2.4 to 2.8 grams of carbon dioxide equivalent per megajoule of thermal (g CO2‐eq/MJth) district heating and from 8.8 to 10.5 grams carbon dioxide equivalent per megajoule of electricity (g CO2‐eq/MJel) to the end user.

[1]  Philip Owende,et al.  A screening LCA of short rotation coppice willow (Salix sp.) feedstock production system for small-scale electricity generation. , 2009 .

[2]  Anna Björklund,et al.  Life cycle assessment of fuels for district heating: A comparison of waste incineration, biomass- and natural gas combustion , 2007 .

[3]  Fredrik Lagergren,et al.  Re-regulating district heating in Sweden , 2002 .

[4]  Kenneth Möllersten,et al.  All CO2 is equal in the atmosphere--A comment on CDM GHG accounting standards for methane recovery and oxidation projects , 2007 .

[5]  Morgan Fröling,et al.  Life Cycle Assessment of the District Heat Distribution System. Part 3: Use Phase and Overall Discussion (10 pp) , 2006 .

[6]  Martin Pehnt,et al.  Dynamic life cycle assessment (LCA) of renewable energy technologies , 2006 .

[7]  Simone Ehrenberger,et al.  Utilisation options of renewable resources: a life cycle assessment of selected products , 2008 .

[8]  Denis Cormier,et al.  Life cycle emissions and cost of producing electricity from coal, natural gas, and wood pellets in Ontario, Canada. , 2010, Environmental science & technology.

[9]  Roberto Dones,et al.  Life Cycle Inventories of Energy Systems: Results for Current Systems in Switzerland and other UCTE Countries , 2007 .

[10]  S P Potter,et al.  Energy supply. , 1973, Science.

[11]  Anders Hammer Strømman,et al.  Life cycle assessment of bioenergy systems: state of the art and future challenges. , 2011, Bioresource technology.

[12]  B. Solberg,et al.  Impacts of policy means for increased use of forest-based bioenergy in Norway : A spatial partial equilibrium analysis , 2007 .

[13]  Ottar Michelsen,et al.  Environmental Impact and Added Value in Forestry Operations in Norway , 2008 .

[14]  H. Chandler.  Database , 1985 .

[15]  E. Hertwich,et al.  CO2 emissions from biomass combustion for bioenergy: atmospheric decay and contribution to global warming , 2011 .

[16]  P. Flynn,et al.  The Impact of Biomass Availability and Processing Cost on Optimum Size and Processing Technology Selection , 2009, Applied biochemistry and biotechnology.

[17]  M. Giugliano,et al.  LCA of domestic and centralized biomass combustion: The case of Lombardy (Italy). , 2010 .

[18]  Morgan Fröling,et al.  Life Cycle Assessment of the District Heat Distribution System - Part 2: Network Construction (11 pp) , 2005 .

[19]  Jeroen B. Guinee,et al.  Handbook on life cycle assessment operational guide to the ISO standards , 2002 .

[20]  Edgar G. Hertwich,et al.  Life cycle assessment of wood-based heating in Norway , 2009 .

[21]  Harrie Knoef,et al.  Handbook biomass gasification , 2005 .