Photosynthesis, Phermentation and Phinances

Different crops offer different energy and ecological returns

Walk outside on any warm day and listen. Not with your ears — those just hear the tractors, the compressors, the quarter-mile pivot creaking its way around the fields. I’m talking about listening with your eyes. Because everywhere you look, the great silent engine of this planet is churning away, converting sunlight, air and water into calories: carbohydrates, proteins, oils, tannins and the whole buffet of carbon-rich compounds that make our farms run.

That engine is photosynthesis — the most reliable renewable energy production system we’ve ever known. Unlike the man-made engines that we dump money into every year, photosynthesis runs on solar radiation, rainwater and air: free inputs. With these basic ingredients, it manufactures the most basic building block of our entire agricultural economy: sugar.

Today everyone’s talking about energy — costs, shortages, resilience, “clean” versus “dirty,” fossil, renewable, nuclear. Somehow, though, it seems like most folks are overlooking the fact that every single green plant on your farm or ranch is using sunlight to split water molecules, then reassembling the carbon, hydrogen and oxygen into sugars. Sugar is fuel. Sugar is the basic building block from which everything else is built.

In the spirit of ecological agriculture — where we design our agricultural systems to mimic the development and functioning of natural ecosystems — let’s examine the biology, the process and the energy economics of ethanol as our primary agricultural product. We’ll look at four very different feedstocks: corn, sugar beets, cattail rhizomes and apples. Each one grows in a specific ecological niche. Each one captures solar energy in a unique way. Each one has its own “phinancials” — the real-world energy return on energy invested.

Photosynthesis: The Original Solar Panel

At its foundation, every plant functions the same way. The chlorophyll in plant cells is struck by photons from the sun. Excited electrons split H₂O molecules, releasing breathable oxygen (O₂) as a byproduct. The hydrogen is used to power the Calvin Cycle, where CO₂ is combined with hydrogen and oxygen to create sugar. Simple. This was drummed into us as sixth graders, so we claim to “know” about it, but the brilliance of the process is noticed by only a few.

The basic photosynthesis chalkboard equation looks like this:

Sunlight + CO₂ + H₂O → Carbohydrates + O₂

But behind that scribble is the first and most important principle of farm economy:

You can’t get more energy out of an agricultural system than the plants themselves can generate through photosynthesis.

If we only sell sugar off the farm (glucose, C₆H₁₂O₆, is produced in every photosynthesis reaction; fructose, also C₆H₁₂O₆, and sucrose, C₁₂H₂₂O₁₁, are reconfigurations of glucose), we lose zero soil nutrients in the crop. The 16+ essential plant nutrients, plus all of the plant’s carbon, get recycled back into the soil to boost fertility for the next crop. All that we’re selling is sunshine and air.

Sugar is not magic. It’s stored sunlight. Although it is the second-largest source of human calories (behind starch), we’re not all going to be able to sell pure sugar. What we can do, however, is mimic nature and reconfigure it into an additional product that has a nearly unlimited market: alcohol. By alcohol, I mean ethanol. Yes, ethanol is the ingredient in adult beverages that causes behavior changes, but more significantly ethanol is fuel — fuel to run internal combustion engines, boilers, turbines, lights and generators for electricity. Anything that gasoline or diesel can do. We can power everything using farm products that leave 100 percent of the plant nutrients in the field where they were grown.

If we’re designing an ethanol-producing system, the best way to do that isn’t necessarily to use the most expensive equipment. It’s to grow the crops that capture the most sunlight and convert it into the most ethanol with the least energy loss in the process.

Different crops package stored sunlight differently. For this, we’ll look at four crops, which is by no means an exhaustive review of the possibilities:

• Corn stores energy primarily as dry starch.
• Sugar beets store it as sucrose dissolved in water.
• Cattails store it in massive, wet, starchy rhizomes with some sugar.
• Apples store energy mostly as sugars, acids and aromatics dissolved in water, with yeast on the skin. Fruits are fermentable juice ready to go.

To design an effective ethanol system, the plant’s ecological requirements should be matched to the land’s natural realities. Swamps grow cattails whether we’re involved or not. Sandy loams near Lake Michigan seem to sprout apples on their own. Deep prairie soils push corn like a geyser. If we match the crop to the ecosystem, we get free solar energy capture. If we don’t, we create another input-dependent system and will be rolling boulders uphill forever.

Phermentation

Call it fermentation if you must, but I like the moonshine-slurred pronunciation — “phermentation” — because it reminds me that people have been converting sugar into alcohol with extremely primitive equipment since long before laboratory thermometers, stainless-steel mash tuns and multibillion-dollar ethanol plants were invented. Lead solder in the old-fashioned stills may have been what caused the slurred speech — at least that’s what Pappy used to say.

The steps are simple:

1. Break down starches into sugars (if necessary).
2. Feed sugars to yeast with no oxygen present.
3. Yeast excretes ethanol and CO₂.
4. Distill the alcohol to the desired purity.

The elegance is in the simplicity. Any farm with a heat source, a vessel and a condenser can distill ethanol. But the real efficiency — the “phinances,” energy in vs. energy out — depends on the crop you choose.

1. Corn Ethanol

Corn is the current king of American ethanol, not because it’s the best crop for producing alcohol but because it’s the most politically entrenched, lobbying-intensive and industrially supported crop in the country. You can’t drive 50 miles in the Midwest without passing dealerships ready to sell you bigger planters, combines, sprayers, fertilizers and the repair bills that go with them.

Equipment needed:

• Tractor with tillage and/or no-till equipment
• Corn planter
• Combine with grain head
• Grain dryer (if needed)
• Hammermill or roller mill
• Cooker and mash tun
• Fermentation barrels/tanks
• Small-scale distillery setup (pot still or reflux still)

The milling, cooking, fermenting and distilling take place at the ethanol plant, and therefore the farmer gets paid for bulk corn. Along with the carbon, hydrogen and oxygen, farmers ship valuable soil nutrients (calcium, phosphorus, potassium, sulfur, etc.).

Yield and alcohol output:

Typical corn yields: 150–230 bushels per acre (varies widely, as we all know).
One bushel of corn (56 pounds) produces approximately 2.8 gallons of ethanol. So, a 200-bushel-per-acre crop yields 560 gallons of ethanol per acre.

Energy balance:

Here’s where things get a little uncomfortable with corn ethanol.
Corn ethanol’s energy return on energy invested (EROEI) is reported to be between 1.2:1 and 1.5:1. That means:

For every 1 unit of energy you put in (tractor fuel, field work, crop inputs, transportation, processing), you only get 1.2 to 1.5 units out. That’s a thin margin at best. And the farmer is not getting paid on net energy yield but on bushels of corn.

Why such a thin energy return?

Corn is an annual crop. It’s equipment-heavy, nitrogen-hungry and fossil-fuel demanding. The combine alone can burn several gallons of diesel per acre just harvesting, not to mention tilling, planting, cultivating or spraying. Drying the grain can take even more.

Corn ethanol works, but it’s not elegant. It’s not lean. It’s not resilient. It’s the ethanol equivalent of growing beef on bagged feed instead of perennial pasture — way expensive for what you get.

It is, however, something you can do today with large, readily available markets. No need to change much on your farm (except remineralizing your soil, minimizing tillage, using cover crops and increasing soil organic matter and biological activity — that’s a given!). Simply divert some of the crop to an ethanol plant. The easiest way to grow ethanol today.

2. Sugar Beet Ethanol

Now we enter the world of high-yield carbohydrates. Sugar beets don’t need enzymes to convert starch to sugar — they already store sugar in its simplest form. That’s free energy courtesy of photosynthesis. Unlike corn, the water demands for making beet ethanol are greatly reduced because the sugar is stored in a nice, juicy beet root.

Equipment needed:

• Tractor and beet planter
• Cultivators or other weed-control tools
• Beet lifter/harvester (modified potato harvester)
• Washer/chopper
• Hot-water extraction tank (for juice)
• Fermentation tanks
• Still

Yield and alcohol output:

Sugar beets can yield 20–30 tons per acre. Average sucrose content: 15–18%. A ton of sugar beets can produce about 20–25 gallons of ethanol.

So, a 25-ton crop yields 500–625 gallons of ethanol per acre.

This is very similar to corn — but with less nitrogen, less equipment and no need for starch-conversion enzymes. Wholesale vegetable farmers already growing root crops can use existing equipment to grow sugar beets. Graziers who use root-heavy cover crops can add extra sugar beets to their seed blend and harvest ethanol as part of a pasture renovation program.

Energy balance:

Sugar beet ethanol EROEI ranges from 1.8:1 to 2.2:1; this can be higher or lower depending on soil conditions and skill of the farmer.

Is this better than corn? Perhaps:

• Less fossil nitrogen is required.
• No grain drying.
• No heavy combines.
• No energy-intensive milling.
• No conversion from starch to sugar.

Sugar beets are a semi–sweet spot for ethanol production: high yield, manageable equipment and decent energy profit since starch need not be converted to sugar, and the water for fermentation is already in the crop.

3. Cattail Rhizome Ethanol

Now we move from industrial agriculture to ecological agriculture. Cattails grow where water lingers — swamps, pond margins, roadside ditches and wastewater lagoons. Cattails are the perfect choice for floodplain fields that regularly experience crop loss due to flooding. They are one of the highest-yielding biomass crops on Earth and thrive on nutrients that wash away in unmanaged runoff from neighboring farms. Cattails clean up the water and scrub excess nutrients from that same water. Floods that destroy a corn crop are just what a cattail crop craves.

This is where ecological agriculture shines: turning a problem (flood-prone fields, excess nutrients, crop failure) into a solution. A waste stream on fields that regularly receive crop loss payments can become a positive-cash-flow, energy-producing system — with the side benefit of improving duck and goose hunting in the fall.

Equipment needed:

• Amphibious root harvester (DIY rigs), or the ability to pump/drain fields before harvest
• Digging forks, potato digger or mint root lifter (common DIY tools)
• Root washer and chopper
• Cook vessel
• Fermentation tanks
• Still

No combines. No 16-row planters. No nitrogen fertilizer. Cattails fertilize themselves with runoff, fish, birds and snails. Many farmers spend hours cleaning cattails out of drainage ditches and field margins now. Instead of paying to remove them, why not harvest them? Immediately after harvest, pigs can be turned loose to hog down the high-energy leftovers.

Yield and alcohol output:

Cattail rhizome yields can reach 10–20 tons per acre of dry matter equivalent in high-nutrient wetlands. Starch content: 45–55% (similar to potatoes). One ton of cattail rhizomes can yield 80–100 gallons of ethanol. So, an average 15-ton stand can potentially produce 1,200–1,500 gallons of ethanol per acre.

That’s not a typo. Cattails rival sugarcane in ethanol yield on the right sites.

Energy balance:

Because cattails require:

• No irrigation
• No fertilizer
• No tillage
• Minimal mechanization
• Marginal or nuisance land

EROEI values of 3:1 to 5:1 are realistic. In some wastewater-fed systems, it can exceed 7:1 because the plant grows while purifying water. This is the ethanol version of letting pigs eat acorns in an agroforestry system instead of buying corn and soy for a feedlot.

4. Apples (Cider Ethanol)

Tree crops are perennial sunlight collectors. Once the system is established, it captures sunlight year after year while increasing in yields up to mature levels in 20 or 30 years. No plowing, seeding, cultivating or buying annual inputs is necessary. Since the fruit is not intended for human consumption, it doesn’t need to be cosmetically perfect, so pest and disease controls can be reduced to near zero. When you apply avoided costs year after year, that’s ecologically compounded interest.

Apple ethanol is simply distilled hard cider — a tradition as old as American agriculture.

Equipment needed:

• Orchard tools (pruners, saws, sprayer if conventional)
• Harvest equipment (shakers, bins, ladders or grazing animals for drops)
• Cider mill (grinder and press)
• Fermenters
• Still

No annual planting. No tilling. No grain dryers. Yeast is on the skin.

Yield and alcohol output:

A mature, well-managed orchard can yield 20,000–35,000 pounds of apples per acre, around 1,000 bushels depending on variety and density. (I never got that much — what the heck?)

Ethanol output from apples averages:

• About 3 gallons of cider per bushel
• 10–20% sugar by weight
• Approximately 5–10% ethanol depending on variety

A typical orchard could produce 300–700 gallons of ethanol per acre.

Energy balance:

Perennial systems shine here. EROEI can reach 4:1 to 6:1.

The trees do the work:

• They capture solar energy seven months a year.
• They maintain their own root systems.
• They build soil instead of mining it.
• They allow for multi-storied cropping with fruit above and livestock (cattle, sheep, hogs) grazing below, with mushrooms growing on prunings and wood chips.

A well-managed permaculture orchard producing ethanol is arguably the most ecologically elegant system of the four — though not the highest yielding in gallons.

Some disadvantages with fruit-based systems (and cattails) are that there is no ready-made apple-based fuel ethanol industry in the country. You can sell your corn or beets to a processor, but if there are apple or cattail fuel plants in North America, I’ve not seen them yet.

Comparing the Four Systems

Feedstock	Gallons Ethanol per Acre	EROEI	Notes
Corn	~560	1.2–1.5 : 1	High inputs, low margin, large ready markets
Sugar Beets	500–625	1.8–2.2 : 1	Strong yields, moderate inputs, large markets
Cattails	1,200–1,500	3–7 : 1	Grows on waste land, minimal inputs, DIY markets
Apples	300–700	4–6 : 1	Perennial, high ecological value, large fruit markets

Phinances: What Actually Makes Sense on Your Farm?

• If your goal is gallons, cattails win.
• If your goal is perennial stability and multiple revenue streams, apples win.
• If your goal is compatibility with existing equipment and massive markets, corn wins.
• If your goal is the best compromise, sugar beets win.

I didn’t write this article to say one way is better than the others. I wrote it to show that not all ethanol is created equal. If we’re looking to create a truly ecologically based agriculture and economy, then we need all of the above options and need to continue developing the underdeveloped ones. Economy is an energy relationship. Ideally, we want the lowest energy input for the energy output. Therefore, the best ethanol system works with the land’s natural tendencies and functions as a perennial ecosystem.

Corn forces the land into a narrow annual row-crop cycle. Cattails respond to waterlogged lowlands. Apples partner with rolling hills, frost zones and deep-rooted carbon cycles with animals integrated into the landscape. Sugar beets thrive in fertile, well-drained soils.

A resilient farm doesn’t choose one — it chooses the ones that fit within the farming system.

Picture it:

• Cattails cleaning the farm’s drainage swales and turning nutrient runoff into fuel.
• Apples on the uplands, providing perennial carbohydrate flow and shady silvopasture grazing.
• Sugar beets rotated through the best annual fields with legumes and grains.
• Corn only where the soil, biology and equipment justify its cost. If you’re currently set up to grow corn, corn ethanol is a no-brainer. If you aren’t, start with a higher-energy system that transitions further into a perennial system.

A diversified ethanol system isn’t just about fuel — it’s about cash flow resilience, biological integration and using the land’s natural energy capture mechanisms. How can we reduce dependencies on external inputs while improving our soils and having enough income to live a good life?

Final Thoughts: Stored Sunlight, Grown Wisely

Every drop of ethanol is stored sunlight. Every gallon you distill is a measure of how well your farm captured solar energy and how wisely you converted it from glucose into a usable or saleable product.

Corn ethanol is the industrial model: established industry, high cost, low margin. Sugar beet ethanol is the transitional model: high yield, respectable efficiency. Cattail ethanol is the ecological heavyweight: high yield on low inputs, nature doing the lifting. Apple ethanol is the understandable model: long-term stability, soil-building, diversified income.

For Acres U.S.A. readers — and for the young eco-ag entrepreneurs stepping into a changing world — the message is simple: Choose crops that partner with the ecosystem, not fight it. Choose energy systems that build soil instead of burning it. Choose phinances that leave money in your pocket and carbon in the ground.

Photosynthesis is the master engine. Phermentation is the conversion system. Your job is to design the landscape where both processes can run on free solar power — with minimal diesel, minimal fertilizer and maximal ecological sanity.

In the long run, the farms that thrive will be the ones powered not by fossil fuels, but by sunlight, carbon, hydrogen and oxygen — the three oldest friends we’ve ever had.

Mark Shepard is a land designer and consultant and is the author of Restoration Agriculture, Water for Any Farm and the Water for Any Farm Technical Manual.