Methane collection?
Usually biofuels are vegetable oils. It is essentially solar power, and you need a lot of land to make it worthwhile, which puts strain on food production and water supplies, and I suspect that growing and transporting it requires more energy on our part than is produced. I don't have the figures, but it is not at present particularly viable. Methane biofuel is most useful as a low-tech solution where other options are not available.
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