Integration of biofuel and DH production – Possibilities, potential and trade-off situations: A review

•In this study integration of biofuel and district heating production is discussed.•The focus is on economic aspects and effects on global GHG emissions.•Trade-offs influencing integration are identified.•A system approach is required to evaluate profitability.•A system approach is required to evaluate effects on global GHG emissions. There are several barriers to increased use of biofuel in the transport sector (e.g., shortage of feedstocks, high production costs, and relatively low energy yields from standalone biofuel plants). One possible solution is integration of biofuel and district heating (DH) production. This study aims (1) to identify challenges (e.g. trade-offs) related to integration and to suggests possible ways of dealing with these challenges, (2) to highlight factors that may influence effects on global GHG emissions from integration, (3) to highlight factors which should be considered when evaluating economic aspects related to integration. After conducting a systematic review using a prescribed and structured protocol, 38 articles were identified as relevant for this study. These articles present four different approaches for integration: delivering the excess heat from biorefineries to DH networks, utilising DH in biofuel production processes, integrating biofuel production with existing DH facilities, and building new polygeneration biofuel production facilities in DH systems (DHS). If investments in biofuel compete with combined heat and power (CHP) production, the electricity price and the premium paid for renewable electricity influence profitability in CHP plants investments and therefore even profitability in investments in biofuel production. Competition should also be considered when weighing environmental benefits (the influence on global GHG emissions). Competition can create trade-offs related to DHS’s operating conditions, limited local and global biomass availability, and limited available heat sinks. To deal with these trade-offs and to avoid suboptimization, stakeholders in regional planning, investors and policymakers should cooperate. All identified studies noted that a comprehensive approach is needed to evaluate profitability aspects and effects on global GHG emissions. For instance, utilising excess heat or residues from a biofuel production process in a DHS requires consideration of alternative DH production and alternative fuels. If electricity is one of the by-products from the biofuel production, alternative elec