Contemporary combined heat and power (CHP) systems are often based on fossil fuels, such as natural gas or heating oil. Thereby, small-scale cogeneration systems are intended to replace or complement traditional heating equipment in residential buildings. In addition to space heating or domestic hot water supply, electricity is generated for the own consumption of the building or to be sold to the electric power grid.
The adaptation of CHP-systems to renewable energy sources, such as solid biomass applications is challenging, because of feedstock composition and heat integration. Nevertheless, in particular smallscale CHP technologies based on biomass gasification and solid oxide fuel cells (SOFCs) offer significant potentials, also regarding important co-benefits, such as security of energy supply as well as emission reductions in terms of greenhouse gases or air pollutants. Besides emission or air quality regulations, the development of CHP technologies for clean on-site small-scale power generation is also strongly incentivised by energy efficiency policies for residential appliances, such as e.g. Ecodesign and Energy Labelling in the European Union (EU). Furthermore, solid residual biomass as renewable local energy source is best suited for decentralised operations such as micro-grids, also to reduce long-haul fuel transports. By this means such distributed energy resource technology can become an essential part of a forward-looking strategy for net zero energy or even smart plus energy buildings.
In this context, this paper presents preliminary impact assessment results and most recent environmental considerations from the EU Horizon 2020 project "FlexiFuel-SOFC" (Grant Agreement no. 641229), which aims at the development of a novel CHP system, consisting of a fuel flexible smallscale fixed-bed updraft gasifier technology, a compact gas cleaning concept and an SOFC for electricity generation. Besides sole system efficiencies, in particular resource and emission aspects of solid fuel combustion and net electricity effects need to be considered. The latter means that vastly less emission intensive gasifier-fuel cell CHP technologies cause significant less fuel related emissions than traditional heating systems, an effect which is further strengthened by avoided emissions from more emission intensive traditional grid electricity generation. As promising result, operation "net" emissions of such on-site generation installations may be virtually zero or even negative. Additionally, this paper scopes central regulatory instruments for small-scale CHP systems in the EU to discuss ways to improve the framework for system deployment.
Biomass-fueled combined heat and power systems (CHPs) can potentially offer environmental benefits compared to conventional separate production technologies. This study presents the first environmental life cycle assessment (LCA) of a novel high-efficiency bio-based power (HBP) technology, which combines biomass gasification with a 199 kW solid oxide fuel cell (SOFC) to produce heat and electricity. The aim is to identify the main sources of environmental impacts and to assess the potential environmental performance compared to benchmark technologies. The use of various biomass fuels and alternative allocation methods were scrutinized. The LCA results reveal that most of the environmental impacts of the energy supplied with the HBP technology are caused by the production of the biomass fuel. This contribution is higher for pelletized than for chipped biomass. Overall, HBP technology shows better environmental performance than heat from natural gas and electricity from the German/European grid. When comparing the HBP technology with the biomass-fueled ORC technology, the former offers significant benefits in terms of particulate matter (about 22 times lower), photochemical ozone formation (11 times lower), acidification (8 times lower) and terrestrial eutrophication (about 26 times lower). The environmental performance was not affected by the allocation parameter (exergy or economic) used. However, the tested substitution approaches showed to be inadequate to model multiple environmental impacts of CHP plants under the investigated context and goal.
