
Farmers Are Using Food Waste to Make Electricity - Bhilai
https://www.npr.org/sections/thesalt/2019/11/30/783001327/chew-on-this-farmers-are-using-food-waste-to-make-electricity
======
darksaints
This is fun cause I've got a side project going on that does this, but without
decomposition, and with direct electrochemical conversion. It uses solid oxide
fuel cells, which can not only consume hydrogen, but can also generate
electricity from the CO->CO2 oxidation. My current work is on developing a
gliding arc plasma reactor that can take solid waste and convert it to syngas,
which is then desulferized and fed directly into the SOFC. I'm hoping to build
a 5-10kw system partnering with an SOFC manufacturer.

I'm a sailor and I'm targeting the sailing cruiser community with it, although
I recognize potential markets elsewhere. The idea is that when you are remote,
in locations where supply chains and infrastructure are undeveloped, it is
incredibly risky to rely on ICEs for auxiliary propulsion and electricity. You
may not have access to gasoline or diesel in the quantities or narrow quality
specification that ICEs require. And you certainly don't have access to fuel
when you are at sea on a long passage. This system would allow you to use
pretty much any conventional fuel, but it would also allow you to use
biowaste, garbage paper and plastic (including ocean plastics), wood pellets,
and even wet biomass like seaweed (the moisture content reduces efficiency,
but is still net positive for energy generation). And it can produce energy on
demand, instead of waiting around for it to decompose and produce methane.

~~~
pstuart
That is fascinating and could be a real game-changer. Would you care to share
more about this?

~~~
darksaints
I'm using some of the research done by Drexel's Plasma Lab [0] as inspiration
for the reactor design. There are lots of plasma reactors out there, in
research as well as commercially available, but most of them are focused on
breaking down gaseous or liquid matter. The research I've seen at Drexel was
the first I've come across that focused on solid fuels. I have a friend who
was an atomization engineer for a rocket fuel company who has some pretty good
ideas for handling solid fuels that we're going to experiment with. But at
least we know it is already possible.

As far as the desulfurization and SOFC is concerned, we're not even close to
that stage yet. Desulfurizers are pretty common, but most SOFC designs tend to
be extremely large and heavy, more suitable for stationary generation. I'd
like to work with NASA's Bi-Electrode Supported Cell concept, which has power
densities suitable for transport applications [1], even better than most
diesel engines. They are actively licensing the technology non-exclusively, so
maybe we could get a license and produce it ourselves, but this is all
bootstrapped so that is probably out of reach in the short term.

[0] [https://drexel.edu/nyheiminstitute/researchlabs/plasma-
energ...](https://drexel.edu/nyheiminstitute/researchlabs/plasma-energy-lab/)

[1] [https://technology.nasa.gov/patent/LEW-
TOPS-120](https://technology.nasa.gov/patent/LEW-TOPS-120)

~~~
toomuchtodo
Have you considered working with S4 Energy/InEnTec to commercialize (they
previously were a JV with Waste Management)? They've done some work in large
scale gasification.

~~~
darksaints
InEnTec looks interesting, looks like they're already working on plasma
gasification. One of the problems I have run into with a lot of companies that
I've contacted is that most of them are only interested in industrial scale
systems, and have no interest in small scale production. Definitely worth
getting in touch though.

------
unglaublich
This is a very common technique that has been in use for decades at farms all
over the world. You can see these dome-shaped containers when you drive
through the countryside in western Europe. The first Wikipedia entry (2002)
mentions that it's a popular process in the Netherlands and Denmark.
[https://en.wikipedia.org/w/index.php?title=Biogas&oldid=2064...](https://en.wikipedia.org/w/index.php?title=Biogas&oldid=206443).

~~~
adwww
My memory is fuzy on the details, but I think this is something to do with Mad
Cow Disese (BSE) being caused indirectly by the old practice of feeding food
waste (containing meat) back to animals as pigswill.

When this was banned suddenly there was a lot more food waste, and also animal
feed became more expesnive, and anaerobic digestion emerged as a solution to
both problems.

~~~
ZeroGravitas
In Australia some farms installed these as a response to the carbon tax. I
believe they got taxed on escaping methane if they let it decompose in the
air, so it was a double win, turning a tax liability into a profit centre.

~~~
mkj
Australia doesn't have a carbon tax though!

It's been a running theme over the past decade's various changes in Prime
Ministers. A bit of a rundown [https://www.afr.com/politics/federal/how-the-
coalition-becam...](https://www.afr.com/politics/federal/how-the-coalition-
became-a-lightning-rod-for-climate-rage-20191113-p53aco)

Edit: oh oops. I'd forgotten it had actually existed for a while

~~~
ZeroGravitas
Not sure if you know this and are joking, but for the benefit of others, it
got introduced and revoked by a following government:

[https://en.m.wikipedia.org/wiki/Carbon_pricing_in_Australia](https://en.m.wikipedia.org/wiki/Carbon_pricing_in_Australia)

------
ZeroGravitas
Semi-related, one comparison I'd like to see is pre-sliced fruit in plastic
containers versus the whole fruit.

These regularly get attacked as signs of how wasteful we are (which I
generally agree with) and people defend them because people with various kinds
of physical impairments might find it hard to peel a fruit.

But I think if you recycle the skins/seeds/waste properly in a factory, wrap
it in lightweight plastic and account for the reduced shipping weight, then
you might come out ahead even if you ignore the benefits of eating more fruit.

One of the many complex decisions that a carbon fee might simplify by guiding
people towards doing the right thing at every step in the process.

~~~
simlan
Puuh i think you overestimate the usable energy from pulp. Honestly anaerobic
digestion works best with simple sugars. More complex carbohydrates and
proteins and their turnover to methane depends on the digestability by the
used bacteria. This is also why corn is a major feed for digesters in central
Europe.

~~~
darksaints
Cellulosic biomass may not have the hydrogen necessary to break down into
methane reliably, but that doesn't mean it can't be used. It can be burned
directly or turned into pellet fuel quite easily.

------
raleec
Also in use since the 80's in various African countries...
[http://www.songhai.org/index.php/en/home-
en/16-songhai/190-b...](http://www.songhai.org/index.php/en/home-
en/16-songhai/190-bioenergie-en)

The Songhai Center does a full carbon cycle re-use. An interesting place to
visit too!

------
energ8
A previous comment on HN went something along the lines of "what is going to
happen in the summer when we've built solar/wind/etc to fulfill this winter
months needs?"

I started researching energy storage. Creating liquid fuels from electricity
would be handy for storage. There are processes, but getting CO2 and H2 to
create hydrocarbons is currently very energy intensive. On the CO2 side, I
think biogas can help this out. biogas is 25-50% CO2. In biogas upgrading, CO2
is considered a waste product (with purer methane the desired output). CO2
from this source looks noticeably less energy intensive than direct air
capture.

I know biogas can be done on the small scale (e.g. homebiogas.com). My
research focused especially on liquid fuel creation that could work in
someone's backyard. I haven't found it. "High‐Selectivity Electrochemical
Conversion of CO2 to Ethanol using a Copper Nanoparticle/N‐Doped Graphene
Electrode" [0] was an exciting find, dampened after reading how well ethanol
stores.

I mostly became convinced that existing oil, gas, and chemical companies will
maintain dominance producing many of the same outputs, from a different
(renewable) set of inputs.

[0]:
[https://onlinelibrary.wiley.com/doi/full/10.1002/slct.201601...](https://onlinelibrary.wiley.com/doi/full/10.1002/slct.201601169)

~~~
darksaints
Looks like you've been going down a similar path as me. Unfortunately, liquid
fuels from pure electricity is extremely energy inefficient. For example, the
fischer tropsch process will consume the hydrogen that you've split with
precious electricity, and only half of that will make its way into the fuel,
the other half of ends up converting back into water. And that is before you
figure out how to get CO2 in concentrations high enough to be cost effective.

You might want to check out plasma reforming. It's the path I'm currently on,
although targeted for a different end product.

[https://drexel.edu/nyheiminstitute/researchlabs/plasma-
energ...](https://drexel.edu/nyheiminstitute/researchlabs/plasma-energy-lab/)

~~~
energ8
Yeah, FT looked insane, which is one of the reasons the linked paper was so
attractive. Ethanol from CO2, electricity, and water at ambient temperature
and pressure.

I mostly think I have to be doing some chemistry/math wrong, based on how not
terrible the energy efficiency is. I'd love corrections or reading material,
as this is not a knowledgeable area for me. \- 2 CO2 + 9 H20 + 12e- -> C2H5OH
+ 12 OH- = 0.084 V \- over voltage of 1.2 V is best \- 1kWh @ 1.2V yields 30
moles electrons \- 30 moles electrons has theoretical yield 2.5 moles ethanol
= 0.146 L ethanol \- reduced to appx 116ml ethanol due to selectivity \- 116ml
ethanol has raw energy of 778 Wh, probably 550 Wh recoverable with Combined
Heat and Power

I think 55% round trip efficiency for energy-dense long term storage would be
big. Of course, this isn't that (math is partially based on theoretical bests,
ethanol isn't long term, CO2 capture and material movement not accounted for).

Thanks for the plasma reforming tip!

------
acd
Biogas you can also use it to run vehicles it has cleaner exhaust emissions
compared to other fuels Gasoline/Diesel. Farmer could and probably will run
their tractors off Biogas. Because farmers like to experiment, its available
and decision paths to get it into action are short.

~~~
fastbeef
No need to experiment, this is already done commercially on a massive scale.

"Stockholm Vatten's sewage treatment works produce 4.1 million m³ of biogas
annually, but have the capacity to double this amount." [1]

[1] [http://www.stockholmvattenochavfall.se/en/water-and-
wastewat...](http://www.stockholmvattenochavfall.se/en/water-and-
wastewater/wastewater/waste-products/)

------
agumonkey
Not too unrelated, composting can generate heat around 60°C. Could save some
heating

~~~
sarcher
I used to work in AD/Composting and the issue I've read about with compost
heat recovery was the cost of the recovery system (compost piles are very
large) and short equipment life span due to damage by loaders/environmental
degradation.

The most consistent use of compost heat has been to ensure proper pathogen
reduction in certain waste materials such as wastewater byproducts. A popular
example of this is called a 'dutch tunnel' (add 'composting' to that if you
google it) where you have a pretty robust, loader accessible composting
container which largely self-heats for pathogen reduction. I use the term
'largely self-heats' because there are aeration/mixture characteristics that
are required for proper temperature development.

Searching EPA 40 CFR 503 is a good introduction to the process, because there
is been a lot written about it and you can easily find guides/introductions.

------
z92
Unanswered question, where does the remaining waste from the plant go? Surely
not all of the mass is converted into gas. And with 1000 tons per day, there
should be a lot of waste to dispose off somewhere.

~~~
jsilence
Anaerobic biodigesters are very common here in Germany. The residue is a
really good fertilizer that can be applied to the fields. At least here in G
the nitrogen application from this has to be documented and subtracts from the
N fertilizer budget farmers are allowed to apply.

~~~
usrusr
The only downside is that to the best of my knowledge, those installations
tend to be designed without storage in mind, running the generator at whatever
time is convenient thanks to flat feed-in rates. Making them dispatchible
would be by far the single lowest-hanging fruit in the whole field of grid
storage.

(Correct me if I'm wrong, I'd love to be)

~~~
adrianN
They provide such a minuscule amount of power that I'm not sure whether making
them dispatchable is worth the effort.

~~~
usrusr
Take a look at [https://energy-charts.de/power.htm](https://energy-
charts.de/power.htm) : pumped storage peak discharge hardly ever reaches a
level of contribution as high has biomass and that is basically all the non-
fossil dispatchability that we have. Meanwhile, biomass is running as baseload
more stubbornly than even nuclear.

Making the biomass contribution dispatchible would be huge.

