[ggm]

I may be wrong, but I believe the british experience with biofuels is that although you want to believe its surplus byproduct, the cheapest source is often grown to be fuel for a biofuel generator. It's like soy/corn for ethanol, it isn't sufficiently profitable to do this solely with waste product, you get better margins growing to fulfill the contract.

[renhanxue]

That may be true in many places, but the Swedish forestry industry is very big, and the district heating plants really do burn mostly forestry byproducts. Of all the biofuel used in Sweden (not just for energy generation), 75% comes from forestry products, and the vast majority of it is either unrefined wood products or byproducts from Kraft process paper manufacturing (like tall oil and turpentine etc).

Specifically in district heating, 87% of the forestry-sourced fuel is unrefined wood products. Almost half of it is just bark, branches and treetops. Of all the biomass in an average mature tree logged in Sweden, 43% ends up as pulpwood, 43% as saw timber, 8% gets burned for fuel and the remaining 6% is treetops and branches which also tend to end up burned for fuel.

There is definitely a lot of debate in Sweden about sustainable forestry practices, though. The industry really wants to clearcut everything for convenience, but it's really bad for biodiversity and the general public hates it.

Source: the report Hållbarare biobränsle i fjärrvärmesektorn, Energiforsk 2023; specifically the charts on pages 14 and 15. Link: https://energiforsk.se/media/33316/2023-979-ha-llbarare-biob...

Addendum: I believe there's also been some studies and experiments involving importing olive pits from the Mediterranean olive oil industry for burning in district heating plants, but I don't think it's been done at scale.

[endominus]

Even if that were the case, wouldn't it still be an essentially net-zero pollution system (disregarding small contributions from transport etc.)?

[tpm]

Depends on the input into growing the biomass. If you are using industrial fertilizers, it's very far from net-zero. Besides that, from my memory there are studies analyzing this and I think they found it's never net-zero.

[youngtaff]

In the British case… it’s being chipped and shipped from Canada and there’s doubts it’s waste wood

It makes more sense to leave trees in the ground than burning them to generate energy