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Comment by legulere | Hacker News Reader

Other than for meat, growing plants for burning uses up a lot of space: wood for burning, biogas, bioethanol and biomethanol. Around 13% of agricultural land is used in Germany for producing biogas for instance. Photovoltaics uses 1/30th of the land.

No new research is needed for this, one would simply need to phase out mandates and subsidies. The money is better used by putting them into the alternatives: Wind and PV for electricity production, heat pumps and electric vehicles for consumption.

Biomass only makes sense if you're using waste products or if you need the carbon like in the chemical industry.

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Is there anything preventing wind power from being above forests? Every wind farm I've seen has been on empty fields but it doesn't seem impossible that you could use the land for crops or even trees.

Efficiency of wind turbines increases with height above 'ground'. I expect for this purpose the top of the tree canopy would be the ground, so turbines would have to be higher by the amount of the forest canopy height, at least. I expect there are more issues with wind flow over tree canopy vs a crop field, but I suspect the height issue alone is enough to make the economics pretty bad.

Not only that, but the trees would provide habitat for all manner of birds which, to not put too fine a point on it, would end up diced by the turbine blades.

The land owner would make more money 1) cutting the trees and selling the lumber, 2) turning the land into farm land or grazing land, and then finally 3) erecting a wind farm than just doing #3 by itself.

Better to situate land-based wind turbines on hills, which usually don't have many trees.

Wait is 3% of Germany covered with photovoltaics?!

Photovoltaic uses around 1/30th of the land to produce the same energy as with energy crops.

3% of Germany covered would already be a lot. A hectare gets you around 500 MWh/a, so a square kilometer gets you around 50 GWh/a. 3% of Germany is around 10000 square kilometers, so you would get 500 TWh/a, which is around the electricity used in Germany in a year.

As a comparison agricultural land is 49%, biofuels are 6.6% of all land in Germany.

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