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> It's expensive but we could absolutely produce green methane with renewable energy. You don't even understand. The methane's mostly for the hydrogen, used to make ammonia or some other nitrogen compound. There are other ways of making this, Birkeland Eyde, for instance, but there like one third as efficient, at best. This means people starve. You might make the case that we could efficiently use livestock manure as a substitute (it's the green solution), but not if you're going to turn this into Planet Vegan. Given the necessity of animal manure, it's difficult to think that "get rid of all the livestock" stems from anything other than bizarre vegan tendencies. If you absolutely have to get rid of the livestock, so be it, but then you really do need the fossil fuels. Pick, it's one or the other as far as I can tell. > And there are natural fertilizer paths that aren't cattle. Nope. You've got livestock (hogs, poultry, etc), or you've got fossil-fuel-based Haber-Bosch. I'm not even really aware of any science fiction concepts "other paths". |
Additionally, pulse crop rotation is increasingly being used to provide some free nitrogen to the soil.
Bioreactors with Azotobacter vinelandii are showing promise in providing nitrogen fixing in a reactor.
And like, industrial composting produces fertilizers with plenty of nitrogen. Soybeans, in particular, need no nitrogen inputs and produce plenty of both useful food and nitrogen containing plant matter.
Our wastewater also contains tons of nitrogen, both from biosolids and from agricultural runoff. These are difficult to get at safely, admittedly, but not impossible.
If you pause to think about it, all that manure needs to come from feedstock plus other inputs (water, etc). If you diverted that same feedstock into producing fertilizer (in the case of soybeans) or not producing at all (in the case of dent corn) you'd have plenty of material and a reduced demand. Manure doesn't just magically come from no inputs.