The Pathways To Biofuels: A Survey Of Why We Should Stop Fretting

Recently, Ivo Sarjanovic, non-executive board member, agricultural commodities professor in Argentina and Switzerland, and venture capitalist agtech investor, reached out to ask me a really good question, one that I should have answered in writing before now. He’d been looking at and listening to my thoughts on biofuels and noted that I had said that there were seven or eight pathways to them, but never listed them. So he asked what they were. When I finally got around to it, it turns out there are ten that I’m aware of, at least the way I count them.

As a reminder or an introduction, here are the basics of my thinking. The first thing is that the only places we will need significant amounts of biofuels is in longer haul aviation and marine shipping. All ground transportation will simply electrify, although the USA’s rail fleet will take longer because of the dysfunction, arrogance, and stupidity of the US rail industry. We’re not going to replace the absurd amounts of fossil fuels with other burnable fuels, we’re simply going to grid-tie everything that we can and put batteries in the rest, with some bridging in a couple of places like longer haul trucking as this works its way through.

And all heat will electrify too. As I noted recently, electrifying heating and transportation in the USA would cut about 50% of primary energy demand. There are no forms of industrial heat that I’ve been able to find after a decade of poking at the subject that cannot be met with electric heating solutions, so there’s no need to burn stuff in industry in the future that I’ve been able to discover. The same arguments of end-to-end efficiency apply for heat even more strongly than for transportation, as heat pumps are suitable for so vastly much of the requirement and are 3-7 times as efficient as burning stuff, and burning stuff is more like a sledge hammer compared to the big tool chest of electrical heat.

And in this future world of biofuels for longer haul aviation and marine shipping, the heavy lifting will be done, I think, by stalk cellulosic (#1) technologies to make ethanol, which will be upgraded to biokerosene and biodiesel. That technology takes the stalks of wheat, grain, and rice, and instead of burning them or letting them rot in middens, puts them into fermenters and distillers as a valuable feedstock while the ears of the grains are used to feed animals or humans. Dual cropping for food and fuel has both sufficient biomass by itself for all the biofuels we need globally as long as we sensibly electrify everything we can and restrict biofuel use to actually difficult to decarbonize segments of transportation.

What are the basics of this? Well, our ecosystem has plants that grow. They take CO2 from the air and water and nutrients and the ground and make them into hard and soft things that are made up of carbon, oxygen, and hydrogen. Fossil fuels are made of the same stuff, it’s just that the plants grew millions of years ago, and nature did most of the heavy lifting of turning them into useful fuels. We just wash them (coal), take water and some other stuff out of them (natural gas) or refine them (crude oil).

In the absence of millions of years to wait and a desire to stop adding greenhouse gases to the atmosphere, we can do more of the heavy lifting using plants instead of being lazy, cheap, and careless by burning fossil fuels. Making beer has been something we’ve done with fermentation using yeast for something like 8,000 years. Making alcohol using beer equivalents and heat is something we’ve done with distillation for something like 6,000 years. Those processes do the heavy lifting of turning plants into useful precursors for biofuels that we need, then we need to do a bit more to get them to a truly useful place.

So what are the other pathways to biofuels? Ivo asked, I answered via messages, adding a couple more as my Americanos kicked in over the morning here in London as I walked around Hyde Park.

A variant of stalk cellulosic is switchgrass (#2) as a feedstock instead of the stalks of food grains. Switchgrass is just a prairie grass that’s native to North America, but every grassland in the world has something virtually identical to it in function, shape, and biological niche. It grows just fine on semi-arable land that’s not worth doing intensive agriculture on. We have lots of land area, after all. As more and more subsistence farmers move off the land, all that semi-arable land increases in availability. The best of it will end up under intensive agriculture, the rest of it will either go fallow and regreen, be used as grazing land to lower the carbon debt of our ruminant livestock (grass fed beef isn’t just tastier), or be converted to wind farms and solar farms. And when it goes fallow, one of the things we can do with it is ensure it has switchgrass or local equivalents growing on it. Then we harvest the switchgrass every once in a while, push it all into stalk cellulosic systems, and turn it into biofuels. It’s a bit more work than using the stems of grain crops in some ways, because it’s spread wide and far and the ground is more uneven, so while I think we’ll be doing it, I don’t think it will dominate.

Corn ethanol (#3) is an obvious one. It’s a big part of American agriculture, as conservative farmers are fed subsidies by mostly Republican politicians to divert food products that could be used by humans or animals into ground vehicles fuels in blends that barely make the needle on climate change quiver. Take the ear of corn, process it to maximize sugars, ferment it, and distill it, and there’s ethanol. That can be upgraded to useful biokerosene and biodiesel, something it has in common with all alcohols, with various processes.

Historically, corn ethanol has been made with lots of fertilizers, pesticides, herbicides, and fungicides, staples of modern agriculture, but overapplied in many cases because that was cheaper than losing money (read subsidies) on smaller crops. As a result, American corn ethanol has a pretty bad environmental history, but people who attack it are ignoring that all modern agriculture shares that problem, and that lots of work is being done on that.

Ammonia-based fertilizers are made with black or gray hydrogen with lots of carbon debt today and turn in part into N20, a nitrous oxide with a global warming potential 265 times that of CO2. And agriculture has been running on diesel for a long time, so that wasn’t much of a help.

The combination means that when people hear or read ‘biofuel’, they often have an allergic reaction to it based on historical US corn ethanol. As I’ve often noted, here at length in print, seeing climate solutions clearly through biases and missing data is challenging. I encourage everyone who is against biofuels to spend a bunch of time updating their knowledge and confronting their biases.

I’m bullish on agriculture decarbonizing fertilizer and using a lot less of the other products over the coming decades. Green ammonia cuts the massive carbon debt of ammonia-based fertilizers, and precision agriculture, increasingly with electrically powered drones like those from Hylio, massively reduces the amounts required for good yields and the diesel used to spread it. Agrigenetics is working to displace lots of ammonia-based fertilizers as well, with Pivot Bio’s nitrogen fixing microbe hack being a prime example. The figures shared with and found by me indicate that drone-spraying can reduce product requirements by 30% to 50%, avoid soil compaction giving 9% to 55% yield improvements, and Pivot Bio’s microbes are already reducing fertilizer requirements by 25%. They had a million acres of corn under their product and were seeing exactly that when I spoke to them a couple of years ago.

Add in low-tillage agriculture, removal of subsistence and most small-hold, undercapitalized, farmers from the world’s food production, and high-tech agriculture is going to stop being a climate problem. That applies to most of the biofuels pathways, by the way, so not only will agriculture stop being a concern, it will also help with the few places there’s a need for burnable liquids.

Next up is sugarcane ethanol (#4). When I lived in São Paulo, Brasil, the urban air was unexpectedly clear and reasonably sweet. The reason is that all light vehicles in the city of 23 million people were required to be able to run on either ethanol or gasoline. You couldn’t drive as far without filling up again on ethanol — sound familiar, everyone who has ever talked to anyone about electric cars? — but it was cheaper. As a result, most people, most of the time, filled up with ethanol. Or rather, drove into a filling station and waited while one or two of the six or twelve attendants filled up their vehicle, the result of Brasil’s national petroleum company, Petrobras, being a key tool to lowering unemployment rates.

Sugarcane is a great crop for ethanol because is has so much sugar in it. It’s basically a big stalk of sugar, where in corn the sugar is concentrated in the ear. And it grows like bamboo, although they are actually in different plant genuses.

After sugarcane, there’s palm oil (#5). It gets a bad rap due to the low environmental standards, including clear burning plantations in southeast Asia. But that’s cleaning up under a lot of regional pressure too. When I lived in Singapore, I experienced one of the worst periods of reeking smoke from plantation burnings in a long time, the 2013 southeastern Asian haze that blanketed multiple countries. That was so bad that a lot of attention started being paid to cleaning it, and palm oil in general, up.

Neste’s expanded palm oil distillery in Singapore just added about a million tons of sustainable aviation fuel (SAF) biokerosene to its output, and it’s handling a lot more of the palm plant as part of improved processes that have a lot less waste. As prime Changi Airport tenant Singapore Airlines used about 6.3 million tons of kerosene a year for operations pre-COVID, a million tons is not a rounding error.

Next up is turning animal dung (#6) into fuel. Animals, especially herbivores, eat an awful lot every day and a lot of it comes out the other end. It’s barely digested biomass, especially again for herbivores, as anyone who has looked at cow or horse dung knows. Heck, it’s been a biofuel for a long time as it’s been collected, dried, and burned for heat. That animal dung is a climate problem right now, as a lot of it rots anaerobically in the middle of piles or in pig manure ponds and emits a lot of methane, with its global warming potential of up to 86 times that of CO2. Biomethane being a problem is a recent theme I’ve been examining, and I’ll return to it a couple of times in this piece.

There is no reason that it can’t be viable to turn this waste biomass into fuel, and the EU is working on the problem. They are spending some money to work the kinks out of using hydrothermal liquefaction to turn manure into a biocrude which can be refined into SAF biokerosene. These are well known technologies that haven’t been applied to manure before simply because it’s always cheaper to dig up and burn fossil fuels if we are allowed to use the atmosphere as an open sewer. I expect this to be an easy win. And since the EU’s livestocks produces 1.4 billion tons of manure a year, that’s a lot of feedstock.

While the ratio of tons of manure to tons of biofuel are obviously pending results and might be 20:1 or 50:1, once again this isn’t a rounding error feedstock for biofuels.

Next is pyrolysis (#7) of literally any biomass, including wood scraps from lumber mills. Recently a research engineer with Bosch in Germany, Roland Gauch, pointed me at Carbonauten GMBH‘s pyrolysis process and asked if it could work.

The generic pyrolysis process puts biomass into a sealed rotary kiln without any oxygen and heats it up to temperatures between 400° and 700° Celsius. The lack of oxygen means it doesn’t catch fire and burn, turning into ash and CO2. Instead, at the lower end of the range all of the liquids turn into a biocrude and get siphoned off, then the temperature gets turned up and the solids bake down to carbon black.

Carbonauten’s approach is slightly different. It uses static kilns instead of rotary kilns and runs the process more slowly as a result. Then it pairs the kilns, using the waste heat from the high temperature process of one to bake the other in the lower temperature process. And it runs the high temperature process on the biocrude it gets out, with biocrude left over. As a result, the biomass bakes itself, which is obviously pretty energy efficient. That’s not perpetual motion, by the way, although it seems like it.

That said, I haven’t seen independent verification of the energy-mass balances, so am withholding judgment. Further, I’d personally design it to run on electricity and maximize biocrude output rather than wasting it on heat. The takeaway is that getting biocrude and hence aviation and marine biofuels out of biomass with pyrolysis works just fine, and there are a bunch of ways to do it, so we can decarbonize the process easily. Gauch pulled Torsten Becker, Carbonauten’s founder, into the discussion after I’d reviewed the publicly available materials, so thanks to both of them for providing clarity.

The carbon black is mostly used in tires, but is also a pigment, UV stabilizing agent, and insulating agent used in a variety of inks, plastics, and rubbers. There’s a 14 million ton annual market for the stuff that’s currently being fed by carbon black made from fossil fuels, of course, so that’s a 14 million ton market with a CO2e problem that pyrolysis of biomass has a fix for. Burying the carbon black, often referred to as biochar, sequesters the carbon that the plants captured from the air, so there’s an offset and subsidies in play there too.

The relatively small size of the carbon black market and the silliness of depending on perpetual subsidies for burying the stuff means that it’s likely a relatively small contributor, but don’t forget that biomethane component. A lot of the waste biomass that can be shoved into a pyrolysis chamber would otherwise sit around in big piles, and the stuff that isn’t exposed to sufficient air would decompose anaerobically giving off methane.

By the way, you really should go to Carbonauten’s website, as its splash graphic is a lot of fun, and accurate too.

Next up is food waste (#8). A lot of agricultural crops end up rotting in the field due to some market or logistics glitch, also notably producing more biomethane. A bunch more gets bruised in transit and gets thrown out by grocery stores because consumers won’t buy it. Again, biomethane. A bunch more goes home and gets scraped off of plates into the garbage. Again, biomethane.

One study found that a full third of produced food, 2.5 billion tons annually, was simply wasted. There is absolutely no shortage of calories to overfeed everybody in the world. What there is is a colossal waste of calories and an inability of the most impoverished to pay to get them delivered to them. Once again, no shortage of feedstock for the scale of the problem of biofuels if we use them remotely intelligently.

One engineer who didn’t believe my biofuels argument, thinking my statements about food waste were hyperbolic, decided to do some math. He found that his kitchen food waste alone was sufficient to power his part of two long distance flights in his lifetime. That’s just end of the supply chain waste, never mind the massive waste along the way.

Right now, some forward-thinking cities and some motivated human beings divert some food waste to compost, turning waste into fertilizer, which is good. But it’s a rounding error on the scale of the problem. Along the way, there are places where there is a lot of food waste in relatively concentrated areas, and all cities have massive waste with little collection. Maximizing and optimizing biowaste diversion, and shoving it into one or more of the technologies above is completely viable and climate sensible.

Finally, there’s that biomethane (#9) I keep talking about. It bakes off of landfills, hydro dam reservoirs, livestock dung, and piles of rotting vegetation. And our herbivorous domesticated animals belch the stuff. It’s a problem, but that doesn’t mean it can’t be part of the solution. I wasn’t able to find a number for how much this was while whipping up this article, so if someone has a reasonable quality one, please let me know.

Personally, I think a bunch of people have very bad ideas about biomethane as an energy source. Lots of natural gas utilities are using it for greenwashing by injecting homeopathic amounts into their natural gas distribution networks and pretending it’s a solution (yes, FortisBC, I’m talking about you again). Others are intentionally arguing for creating a massive network of anaerobic digesters spread across the countryside to throw biomass into to create a lot more methane in a distributed, leaky climate change-causing system. Europe seems to think it’s a great idea to replace Russian natural gas with biomethane, seeing a 20% increase year-over-year during the crisis.

Intentionally creating more methane when it’s a huge climate problem seems like a terrible idea to me, but perhaps I just don’t like the smell of odorants.

And others, like the methanol industry, are pretending their methanol is zero carbon when they add perhaps 4% methanol made with biomethane to methanol made from natural gas, claiming that the biomethane would have been vented to the atmosphere otherwise, allowing them to claim its GWP of 26 to offset their methanol’s carbon debt of 1.4 tons of CO2e per ton of methanol.

Yes, Methanex actually claimed that when it powered a ship crossing the Atlantic with the stuff, and credulous press actually printed the perversity as a positive. For context, methanol is one of the main contenders for repowering marine shipping, and even at my modest levels of requirement after amplification, if it was the winner, the global methanol market would triple in size, so you can understand the incentives they have to paint their pigs’ lips green.

And I also think job one has to be reduction of biomethane emissions. There are some obvious pathways for this. Animal feed supplements, seaweed-derived Beano for cows, can reduce ruminant belching by up to 80%. Separating that food waste I just talked about and keeping it out of landfills so that it doesn’t rot and create biomethane is obvious. Aerating animal dung piles and ponds so that they decompose aerobically and create CO2 instead of methane is a big win. Burning agricultural waste is a lot better than letting it rot in piles and creating methane. Putting pipes into landfills to vent methane and either capturing it for use, burning it for electricity on site (yes, that’s a thing), or flaring it is a lot better than letting it vent to the atmosphere.

That all said, we have so much biomethane above background creation from natural processes, so much of it is concentrated, and our ability to eliminate it completely is non-existent, so how can we take advantage of it for biofuels?

Well, as I said in a discussion thread with Michael Liebreich and others recently related to his podcast chat with Sir Chris Llewellyn-Smith about building massive salt caverns under the UK and electrolyzing green hydrogen to shove into them for the every ten years when the wind and sun just disappear in northern Europe for a couple of weeks, I’d prefer to just divert as much biomethane as possible into those caverns instead. It’s a waste product that’s a lot less expensive than green hydrogen and is much less likely to leak away.

But then there’s the next question: can we turn methane into a useful biofuel that doesn’t cause global warming when it leaks? Well, yes. I don’t think methanol is it, personally, but I’m not adverse to a biomethanol marine shipping industry if that ends up penciling out and the biomethane is captured from our anthropogenic emissions instead of being manufactured en masse in anaerobic digesters. But methane can be turned into biodiesel and biokerosene through some fun with methanotrophic microbes, bugs that love to eat methane for food and which leave a biocrude behind.

Anywhere there’s a lot of methane, you’ll find a bunch of these bugs, some of which like oxygen in the mix, others of which like an oxygen-free lifestyle. Rice paddies have them, for example.

So take that naturally occurring biomethane, feed it to some bugs that like to eat it, and then turn the resultant mess of biocrude into refineries to make aviation and marine fuel. Seems like a win-win to me. Not necessarily easy or cheap, but a lot more sensible than burning fossil fuels.

Finally, there are variants of some of these processes that add hydrogen to optimize output (I’ll call that #10). Naturally, none of them use green hydrogen today, but obviously they are all claiming that of course they’ll do that. Personally, I think the processes that lean heavily on green hydrogen will end up being uneconomic compared to ones that use less or none, hence my projection of only four million tons of hydrogen for supplementing biofuel production in 2100. That’s an informed guess though, as I haven’t done the math on the processes with and without hydrogen supplementing.

As I said at the beginning of this piece, I think stalk cellulosic ethanol to biokerosene and biodiesel processes will dominate the market. It’s been a commercialized technology for a decade, the waste occurs in specific times and has to be separated from the differently useful part of the plant by machinery, and there are a few obvious ways to optimize it, including rebalancing our grain crops to be less ear-heavy and have a bit more heft to their stalks. (What, you thought our bodybuilder-who-neglects-leg-day grains were remotely natural?) The combination of concentrated time, concentrated locations, and automation seems like a winner. There’s enough of it. But I’m not particularly fussed if it turns out that five of the solutions pencil out as economically competitive in different markets, or if aviation gets one process dominating while marine shipping gets another.

As a side note, a the cleantech VC arm of a Latin American private energy major with billions in annual revenue has engaged me to assist me with their investment theses including a biological pathway, and a European private shipping concern with the same revenue has engaged me to debate maritime decarbonization with internal and external experts in Glasgow, hence my weekend making my feet hurt in London in advance. The timing of Ivo’s question was impeccable, as pulling this piece together has helped firm my thinking and prepare for both efforts.

The point of this survey of biofuels is that there is an absurd amount of biological feedstock that’s currently a methane emissions problem, and having proved there’s enough in only one pathway for what I project is peak global need, I don’t really care how it turns out. To be clear, I’m sure I’m missing pathways. While I’m well informed, pay attention, and know that the meaning of research does not mean watching YouTube videos or reading Facebook groups, that doesn’t mean I pretend to omniscience. I’m sure there are at least a few viable pathways I haven’t noticed yet (as well as a bunch of nonsense that I’ll likely be inundated with based on this piece). Regardless, we have enough waste biomass feedstock to fulfill all of our transportation needs, and the market and a bunch of bright people will figure out which ones are cheapest and lowest impact.