Beyond Biomass: Assessing Heat Pump and Hybrid Based Alternatives for Decarbonising District Energy Systems

In its decarbonization strategy, the European Commission relies on biomass to reduce emissions in
sectors such as heating and transport. In 2021, biomass accounted for 59 % of renewable energy
consumption in the EU. However, its large-scale use raises two major concerns. First, the claimed
CO2 savings may translate into a carbon debt, which is incompatible with the urgency of climate
mitigation. Second, sustainably available biomass resources are limited, potentially leading to a
gap between increasing demand and constrained supply. Additional concerns related to biodiversity
preservation can also be raised. In this context, some countries, such as the Netherlands, advocate
for strengthening sustainability criteria and limiting biomass use to high-value end-uses, such as
advanced biofuels, and only after higher-priority cascading uses.
Against this background, this work explores alternative solutions to biomass for the heating of a
university campus supplied by a district heating network, based on hybrid systems combining air-
to-water and geothermal heat pumps. Using a multi-energy optimization model for district energy
planning developed by our team, we assess the impact of biomass price, photovoltaic deployment,
thermal storage and battery installation on the optimal system configuration. Key indicators, includ-
ing system cost, self-consumption and biomass savings, are analysed in order to formulate policy-
relevant and operational recommendations.