Background
Renewable energy and biomass are becoming increasingly important energy sources to help mitigate climate change and meet national renewable energy targets. This will lead to a substantial growth in solid biomass consumption for heat and electricity, but questions about its sustainability have been raised. Danish energy companies have addressed these issues with sustainability criteria in a voluntary industry agreement since 2016. The aim of this study was to synthesise and evaluate biomass sourcing in the Danish energy sector and its compliance with voluntary sustainability criteria.

Methods
We collected energy companies’ public industry agreement sustainability reports and compiled the included information into a dataset that allowed us to compare and analyse the Danish energy sector’s biomass sourcing, compliance and implementation of sustainability criteria in 2016 and 2017. Furthermore, we analysed the supply chains and feedstock use of Danish energy companies.

Results
In Denmark, medium to large energy companies documented that 57% and 70% of their biomass sourcing was in compliance with the sustainability criteria in 2016 and 2017, respectively. To show compliance with the sustainability criteria, sustainable forest management certification was most common in 2016 while risk-based certification prevailed in 2017. Most biomass is sourced and reported sustainability compliance by a few large companies. Wood pellets are sustainability reported and sourced in significantly larger volumes than wood chips. Danish energy companies source solid biomass from local to global scales, but especially from countries around the Baltic Sea.

Conclusions
The Danish approach to sustainable sourcing with voluntary sustainability criteria has been successfully implemented for most of the wood sourced for energy by medium to large energy companies in Denmark. The implementation of this approach shows that it has been possible within a couple of years to implement sustainability governance with risk-based criteria for multiple energy companies that source solid wood biomass at the megaton scale. A risk-based approach to implementation of sustainability criteria for forest biomass has also been chosen by the European Union (EU) and will be implemented through the EU Renewable Energy Directive from 2021.