Life cycle assessment of small-scale combined heat and power plant: Environmental impacts of different forest biofuels and replacing district heat produced from natural gas

Abstract

Forest biomass is used in many countries as an abundant and easily accessible source of renewable energy. While forest biomass has certain advantages in terms of carbon sink capability, it cannot be considered an emission-free energy source, and the environmental differences among various forest biomass sources have been unclear. This study uses life cycle assessment for two purposes. The first is to quantify the environmental impacts of the energy production of a small-scale, combined heat and power production plant utilizing different forest biomasses. The second aim is to estimate the change in environmental impacts on district heat production from natural gas when partially replacing it by heat from the combined heat and power plant. The environmental impacts include global warming potential, acidification potential, and eutrophication potential. The calculated environmental impacts of utilizing different forest biofuels in the CHP plant in relation to produced energy are 2.2-5.1 gCO2,eq./MJenergy excluding biogenic carbon emission, 59-66 gCO2,eq./MJenergy with biogenic carbon emission, and 133-175 mgSO2,eq./MJenergy and 18-22 mgPO34-,eq./MJenergy with pellets, showing the highest values. The results indicate that by using forest biomass instead of natural gas in energy production, the global climate impacts are reduced when biogenic carbon is excluded, while the local effects are higher (acidification potential and eutrophication potential). Including biogenic carbon reduces the calculated climate benefit since the total emissions end up being 4-7 % over those of natural gas use. The potential benefits need to be weighed against the possible drawbacks.

Assessment of environmental impact of biomass power plants to increase the social acceptance of renewable energy technologies

“…Havukainen et al. (2018) [55] have calculated the environmental impacts of a small-scale CHP (540 kW) powered with woodchips or pellets. The results show, excluding the biogenic carbon emissions, an environmental impact of 2.2–5.1 gCO 2eq MJ −1 , which grows to 59–66 gCO 2eq MJ −1 with the biogenic carbon emissions.…”

Combining Biomass Gasification and Solid Oxid Fuel Cell for Heat and Power Generation: An Early-Stage Life Cycle Assessment

“…In particular, the literature reports a few life cycle assessments (LCAs) of heat and power from SOFC-based CHPs and several ones of CHPs involving biomass gasification processes but no one on their combination (in October 2019, from Scopus database searching in TITLE-ABS-KEY). These studies provided the following main findings: (1) the investigated CHPs present lower impact in terms of climate change compared to conventional technologies [2,15] and (2) the biomass fuel production has the highest contribution to total life cycle impacts [16,17]. These studies also highlighted several methodological uncertainties of LCAs that can lead to significantly different results.…”

“…Compared to separate production of heat and electricity from fossil fuels, combined heat and power systems (CHPs) can potentially allow for significant reductions of climate change impact [1,2]. In Europe, coupling heat and electricity generation from renewable sources is also one of the most cost-effective decarbonization strategies [3][4][5].…”

“…The environmental LCA presented in this study has a twofold aim: (1) to identify the main sources of the environmental impact of this new technology and (2) to assess its ecological competitiveness compared to the separate production of heat and electricity and one of its main competitors, i.e., Organic Rankine Cycles (ORC). Moreover, this case study is used to analytically discuss the influence of the allocation method in the LCA results for CHP plants and provide methodological recommendations for better allocation practices.…”

Life Cycle Assessment of Different Low-Temperature District Heating Development Scenarios: A Case Study of Municipality in Latvia

“…Havukainen et al [33] in the study about different forest biofuel use and replacement of natural gas in small-scale combined heat and power plant used CML2001 assessment method with impact categories of GWP, AP and EP. The functional unit of 1MJ of produced energy was used.…”