How much fuel do you have to burn to turn that waste food into usable nitrates? If it requires less fuel than the Haber-Bosch process, then why is it not profitable?
Or you can compost it into fertilizer. It isn't profitable because fossil fuels are artificially cheap and aren't paying for the externalized costs of pollution. Also, if you did it right you can also burn food directly as fuel.
Haber-Bosch process isn't a free lunch where free energy just pops into existence.
> " It isn't profitable because fossil fuels are artificially cheap "
Not that cheap. In the aforementioned metal recycling example, the energy is typically coming from fossil fuels too; refining aluminum from ore takes an insane amount of electrical power. Even if you do that with renewable energy, that's still that much power that can't be used for other things that must be supplied by another power source (e.g. fossil fuels.)
A lot of natural gas is stranded or considered a waste product of oil production.
So fertilizer plants in those areas suck up that cheap CH4 to reform it into H2 and heat up the Haber-Bosch process to make ammonia and then into more transportable fertilizers like urea.
> If it requires less fuel than the Haber-Bosch process, then why is it not profitable?
That was clearly intended as a zing, but it just shows you aren't thinking about this right. Conventional ammonia production is vastly less efficient than just composting your garbage. Be real here. Bacteria literally do the job at a labor cost of zero and all you need to do is keep it in a stable environment.
What hurts is what always hurts: scale. If the composting facility is across town, you also need to haul the biomass around and haul the fertilizer back. If the industry is tooled up to spread pellet fertilizer it's going to see an immediate cost moving to equipment that can spread and till compost.
But stop pretending that there's an "efficiency" argument to baking nitrogen into ammonia in a 20 barr, 500C pressure cooker. That's nonsense.
I'm a deep green (I don't eat meat, I don't fly, I don't drive), but I'm also a skeptical green. There is an overwhelming presumption that recycling must be good for the environment, but the evidence is often weak or nonexistent. I'd be more than happy to support food waste recycling if someone can provide good evidence that it actually is environmentally beneficial.
The classic example is plastic versus re-usable glass bottles - plastic nearly always proves to be more sustainable than glass, because glass bottles require vastly more energy to manufacture, they're much heavier to transport, they require surprisingly large amounts of energy to wash and they have relatively short average lifespans. The plastic waste issue is quite effectively solved by just burning it - plastic waste is a perfectly good hydrocarbon fuel.
The key points: Food is the basis of the human economy. Collecting and composting food waste closes the loop and completes the nutrient cycle in the soil we use to grow food.
Not to mention: half the problems we have with traditional dirty landfills is that the unsorted food waste starts to decompose (releasing methane) and creates a hot environment that causes everything else to degrade in a toxic manner. As soon as you take it out, you have a "dry" landfill, where currently unrecyclable single-use things can be stored in GPS-tagged storage sites, until someone finds a better use for them and/or we start to phase them out.
The only relevant data I could find in those links was from "ecologically sustainable recovery of bio-waste". A figure on page 38 suggests that bio-waste recovery could save between 29 and 194kg CO2e per ton of waste, but the breakdown does not appear to include the emissions involved in the collection of domestic food waste and the accompanying text acknowledges that the data is not based on a full lifecycle analysis. I cannot find the source document cited in the figure, possibly because of a translation issue from the original German.
>The plastic waste issue is quite effectively solved by just burning it - plastic waste is a perfectly good hydrocarbon fuel.
How about the pollution caused by burning plastic waste? Take dioxins, for just one example. I've read that they are released when you burn plastic (don't have a link handy).
"someone can provide good evidence that it actually is environmentally beneficial"
I don't think anyone is, just that its less bad than the alternatives.
You don't drive, presumably you walk or cycle then. Each of those activities have negative environmental externalities compared to not doing them, after all you have to consume extra calories. So while each is infinitely better than driving, they aren't environmentally beneficial.
With your plastic v glass example, you seem to be using sustainability in a way that I wouldn't recognise, to me sustainability is about how long you can keep doing something regardless of how much energy it requires (up to a point, and assuming clean energy sources). The glass is infinitely recyclable, the plastic isn't. Especially when burned, so I would say the glass is sustainable.
"to me sustainability is about how long you can keep doing something [...] glass is infinitely recyclable, the plastic isn't"
Exactly - it's about reuse (ie. infinitely recyclable), and the shift in thinking that comes along with that.
Burning plastic releases toxic byproducts into the local environment, and requires us to use more fossil fuel hydrocarbons to make new plastic.
On the other hand, instead of transporting glass bottles across half the country, why not refill them in a local bottling plant, using local produce? Glass bottles can be washed 50-100 times, and after that they can simply be remade into new glass.
In Germany today, there are 5 standard glass beer bottles that everyone uses, so they can be refilled by local breweries all around the country. If a country is thinking of implementing a similar system, it would also be wise to invest in container deposit scheme, to ensure the bottles get returned in a good condition for reuse. Return rates in Germany are upwards of 98%.
It wasn't long ago, when our parents/grandparents/great-grandparents were getting milk delivered in glass bottles, to be washed, refilled and reused. We could easily go back to those more sustainable plastic-free times.
The key mistake of GP and yours here is this part of GP quote you elided:
> regardless of how much energy it requires (up to a point, and assuming clean energy sources)
The world isn't yet powered through clean energy sources in any significant way. Electricity production runs mostly on fossil fuels, and then electricity is currently only a part of the equation - heating and transportation is still mostly powered by burning hydrocarbons pulled from the ground.
It is not just valid, but very important, to consider sustainability in context of system at the whole. Greedy algorithms don't work here. A glass bottle may be "infinitely recyclable", but if doing the actual recycling involves using energy from unsustainable sources, it's not a sustainable behaviour in itself. Sustainability is an end-to-end thing; if any link isn't, the whole chain isn't.
Now that we've established that glass recycling isn't currently a sustainable practice, we can still consider whether it's better or worse than alternative unsustainable practices. Regular "single use, thin plastic bottles, destination: landfill" approach seems idiotic. But alternatives involve "thick, refillable plastic bottles" (something I recall Germany used to do), or "single use, thin plastic bottles, destination: power plant" which isn't as dumb as it sounds - if it could be made the primary fuel source for said power plants, it's a step up. I reserve judgment on the alternatives, as I have no data. And it's kind of a problem today: regular people don't have an easy way to review end-to-end performance of such strategies. So they vote for convenience, or for whatever looks ecologic.
Burning hydrocarbons has still place in a sustainable future - they're a great high-density energy store, after all. But to make the chain end-to-end sustainable, we'd have to be using clean and sustainable sources to take back all the emissions and to manufacture more hydrocarbons.
EDIT: And to be clear, I'm always biased in favour of reusing and (then) recycling. But the energy calculation has to make sense, because sustainability is in big part an energy management problem (the other big part is habitability management problem - not doing net damage to the ecosystem; but, assuming the will to do it, it also quickly becomes a subset of energy management).
Right, I'm talking about technically feasible solutions.
And it is entirely feasible to power the world with clean, renewable energy. We have the solar capacity to meet hundreds of times our current energy capacity (using less land space than our existing roads). And over 530,000 potential pumped-hydro sites worldwide to store that energy (of which we'd only need a tiny fraction). For example, there are 22,000 sites in Australia, of which we'd only need 20. The research shows that cost will be a non-issue.
But we don't currently live in a world that's powered by renewable energy, we live in a world where the vast majority of energy is generated from fossil sources. Making that transition will require decades, billions in investment and a lot of challenging trade-offs.
Here in the real world of 2019, energy is the dominant factor. If we need to dig up landfills to recover materials in 2100, so be it - right now, we have a ticking clock to mitigate the worst effects of the impending climate crisis. We simply cannot afford to waste time on wishful thinking and idealism, we need to cut our carbon emissions hard and fast.
"If we need to dig up landfills to recover materials in 2100, so be it"
You were talking about burning plastic bottles a minute ago???
Agreed we need to minimise energy usage and move away from fossil fuels as quickly as possible, plastic usage risks creating a market for fossil fuels, where petrol/gas become cheap byproducts, so it isn't a straight forward trade off.
The way I see it, we need to optimize our energy use and ecosystem damage output, until we can switch over completely to surplus clean energy. After that, a lot of ecology talk stops to matter. For instance, with surplus energy put to use in collecting, recycling & emission capture, we could use disposable plastics to our hearts' content.
Unfortunately, as you say, widespread deployment of clean & sustainable energy sources comes down to barriers in the economic and political domains. That's why I feel modern ecology needs to optimize for reducing energy use, even if it might mean preferring some locally suboptimal-looking solutions that turn out to be globally more efficient.
I could have written 'glass recycling has the possibility to be sustainable', but instead I wrote 'glass recycling is sustainable assuming X'
You could complain if I didn't state my assumptions, but I did.
I currently buy 100% green electricity, I could use that to recycle glass today and that would be sustainable. So this isn't some hypothetical, it is possible today.
That isn't to say that I disagree with your points though. It isn't an easy problem, and 'best' now, doesn't necessarily match 'best' in an ideal world.
How much fuel do you have to burn to turn that waste food into usable nitrates? If it requires less fuel than the Haber-Bosch process, then why is it not profitable?