brimstoneSalad wrote: ↑Thu Nov 23, 2017 6:00 pm
I believe the majority of the nitrogen in either case is incorporated into the cells of the yeast, so I wouldn't expect it to be substantially different when adjusted for ethanol production. If we could find data on that, that would be great though.
I tried to search for that. So I typed "straw bioethanol company" on Google and found this website:
http://www.sbe.fi/SBEeng/Factory.html
I was surprised to see no mention of DDGS equivalent as side product so I sent them an email to confirm. I have yet to get a response as of now.
But then I saw they mentioned a website named inbicon.com so I visited it:
http://www.inbicon.com/en
It has a page that mentions the end products of straw distillation:
http://www.inbicon.com/en/key-advantages/end-products
So I guess I got my response in advance: the DDGS equivalent is apparently molasses with 5% protein content in dry mass (assuming that's what "DM" means). It's suggested as food for livestock, but also for further fermentation. The lower protein content makes it seem like it would be worse that DDGS as a fertilizer due to higher C:N ratio. Maybe it could be used as feedstock for nutritional yeast? That would mean much less recyclable nitrogen that what I expected, but that's maybe not necessarily a bad thing if that nitrogen ends up directly as human food rather than passing through plants multiple times before we eat it (and possibly return it to the soil if we're using biosolids), as processing agricultural waste that way would increase the amount of edible food without increasing artificial fertilizer use.
Although it expressed concerns related to increased uses in synthetic fertilizer, the second study I linked in my post above still tends to believe that biofuel from agricultural waste would still overall be a win if that biofuel can replace the same amount of petroleum, assuming we're using the right way to get ethanol from straw.
I'm also wondering about nutrient extraction from the ocean, since due to gravity elements necessary for life end up in it. We do mining for things like phosphorus, and even though we probably have a lot in reserve, it might be good to think about extracting essential plant nutrients from sea water. Could seaweed cultivation be a way to do it? Although it is edible, we wouldn't eat directly much of it because it is so rich in iodine and an excess can be dangerous for health, which would mean the rest could be used as fertilizer (or maybe we could process it to remove iodine to safe levels to increase the amount of seaweed that could be directly be eaten by people). It has a high nitrogen content (a C:N ratio of 22:1 in a compost with 82% seaweed and the rest being fiber byproduct of sugarcane processing:
https://www.researchgate.net/publication/275524578_Seaweed_compost_for_agricultural_crop_production) which means it could be effective as a fertilizer if we want to use it as such. However I'm not sure if cultivated seaweed alone could sustainably compensate to give us the phosporus and potassium and other plant nutrients that are inevitably leaking from a nutrient cycle even with biosolids and composted food waste (we should also make sure most of our food waste gets composted rather than rotting in a landfill and releasing methane in the atmosphere). For now it's probably not a huge concern with mined phosphorus, but when reserves are going to run out (maybe not in our lifetimes, but during that of our descendants if humanity is still around in the next centuries) we might need to find a way to harvest it sustainably.
Here's another page that discusses seaweed as fertilizer:
https://www.rhs.org.uk/advice/profile?pid=301
To be fair I'm intuitively not convincing myself that seaweed farming alone could sustain all our needs for phosphorus and potassium, unless maybe we put seaweed farms literally everywhere on coasts but I don't think we would want that. So we also might use other techniques, but they might be more costly in energy, but it looks like it's not impossible as this study suggests:
http://www.sciencedirect.com/science/article/pii/000326709280134S
The total dissolved phosphorus is extracted efficiently by adsorbing it on to iron(III) hydroxide surfaces [iron(III) hydroxide-coated acrylic fiber], following a technique used earlrier for the extraction of dissolved silicon and other trace elements from sea water.
Another topic I want to address is crop rotation. I already described it in the Wiki page, but it looks like there's more nuance than that. Not that it's not beneficial, but it's apparently often impractical, a major reason for monoculture being disparate demand for different crops, plus the fact different climates and environments are most beneficial to different crops. Although not a primary source, it was being suggested by this page:
https://skeptoid.com/episodes/4454
[...] If there was an equal demand for corn, soy, and cotton, farmers would be able to rotate perfectly and everything would be hunky dory.
Sadly that's not the case. In 2011, the United States had 84 million acres of corn; 74 million acres of soybeans, 56 million acres of hay, 46 million acres of wheat, but only 10 million acres of cotton. So many products, both food and industrial, come from these, but the acreage needed from each is so disparate that crop rotation is often problematic. Further complicating it is that each crop grows best in a specific climate zone and soil. It's really, really hard to find two or more crops that are both in equal demand and that will grow well on any given farm's ecology.
Seeing the references it looks like it was most likely taken from this link:
http://www.epa.gov/oecaagct/ag101/cropmajor.html however visiting it redirects me to
https://www.epa.gov/agriculture which means the link is dead. So I searched on Web Archives and found an archived version:
https://web.archive.org/web/20130521220052/http://www.epa.gov/oecaagct/ag101/cropmajor.html
The numbers on the page are correct, but I see no mention of "there is monoculture because demand of all of it is not equal" on this EPA source. It sounds like an educated guess from the one who wrote the blog page, how accurate is that? And because demand for all these things would be different in (and, in the case of crops grown for livestock, probably considerably lower) how would convenience of crop rotation translate in a vegan country? Maybe it would mean a lower overall demand for soy and corn (since they're common livestock feed) making it more on par with wheat, and thus making crop rotation easier or more effective thanks to more similar demand?
Or maybe we might want to develop region-specific varieties for staples like soy and wheat, that grow better in specific regions and climates so different ecology in different zones is less of a constraint for effective crop rotation. I wonder if genetic engineering could be of any help in accomplishing that goal - in which case it would debunk a common anti-GM argument "they genetically standardize all our crops and thus recude biodiversity"
And by the way, I could also add an advantage of crop rotation I didn't mention before - it works as pest management by breaking the life cycle of pests that attack specific crops over others.
Finally I'm glad I did start a Wiki page on sustainable vegan agriculture, because I don't know everything it means I must do my research and that's pretty fun and I learn a lot.
Appeal to nature: the strange belief that what is perceived as "natural" is necessarily safer, more effective or morally superior compared to what isn't.
