☢ Turning Spoiled Food Into Fuel

In today’s newsletter:

• 🌵 The Funky Side of Dragon Fruit

• 🔥 The Big Idea: Turning Spoiled Food Into Fuel

• 💰️ A Reminder: Get a free award-winning heirloom garden

Vampire Blooms:

The dragon fruit (Selenicereus undatus) gets mixed reviews in the flavor department. Here’s one Reddit comment: “Looks awesomely exciting (with a great name!), tastes like wet styrofoam.”

Whether you like dragon fruit or align with the Redditor, I think you’ll agree the plant plays life on hard mode.

It won’t let any bees or butterflies pollinate its flower. Instead, every bloom opens at sundown and closes before sunrise. For one night only, the fate of fruit production relies on moths and bats finding their way to the plant. If nothing comes, the flower shrivels and falls off the cactus.

🔥 Turning Spoiled Food into Fuel

When you think of renewable energy, the first thing that comes to mind probably includes a field of solar panels or a horizon filled with wind turbines.

These are the “sexy” high-tech solutions the news outlets love to cover. They’re important, no doubt about it. I’ve recently gone off-grid with the help of a massive battery bank and solar panels, and my setup is perfect for a mobile lifestyle.

Today, however, we’re looking at one of the least sexy renewables — the kind that the news sparingly covers because it’s dirty, it’s smelly, and it belongs in the realm of Mike Rowe.

Hopefully, you’ll finish reading this with a different perspective. We’re on a mission to make ‘Biogas’ the next ‘Brangelina’.

Reclaiming Our Food Waste

Most sources estimate the US discards around 40% of all the food it produces.

In other words, that means we Americans throw out roughly 133 billion pounds of food annually. The EPA’s 2010 estimates say that the average person sends nearly 220 pounds of food waste to landfills every year. That figure doesn’t include retail operations like restaurants.

What happens to all that food?

The EPA suggests that food waste produces 170 million metric tons of CO2 equivalent (million MTCO2e) each year without including the methane emissions from landfills. And municipal solid waste (MSW) landfills are the third-largest source of methane emissions in the US — accounting for roughly 14.5% of human-related methane emissions in 2020.

You don’t need to know what these numbers mean. They’re only relevant as a signal of what we’re forgetting when we throw food away:

We buy food for its energy. That energy doesn’t suddenly disappear from an apple core when we slice it out, nor does it vanish when the first spot of mold grows on some bread.

When food ‘spoils’, we’re really looking at a dish that another species chose to dig into before us. And as we strip fat, protein, carbohydrates, vitamins, and minerals from our food, so too do the sneaky little microbes populating our stinky yogurt.

The gasses that escape from our massive landfills stem from the indulgent feast we stuff in the ground for those less-picky organisms.

In many ways, the landfill becomes a giant “digestive tract” to break down the abundant nutrients. The similarities to our gut don’t stop there.

The methane that leaves landfills is the same methane that leaves animals when they ‘break wind’. We owe that shared experience to a subgroup of bacteria and archaea called Methanogens. Those methanogens consume sugars, amino acids, and other molecules under anaerobic conditions (without oxygen). The byproduct of their ‘meals’ is methane, the greenhouse gas that has more than 80 times the heating potential of carbon dioxide for the first twenty years it’s in the atmosphere.

Sounds potent. What’s the fix?

As many childhood cartoons like to point out, flatulence (methane) is flammable. It’s present in fuels all around us. For example, methane is the dominant hydrocarbon in the natural gas used to power stoves, water heaters, and other household appliances.

The current practice of dumping food waste into landfills is the equivalent of turning the kitchen stove on without lighting it. We’re wasting millions of tons of gas.

To resolve the issue, we need a way to capture the methane from our decomposing organic waste before it escapes into the atmosphere.

In most cases, that means we need a biogas digester.

Biogas Digester = External Stomach

Digesters come in many shapes and sizes, depending on the volume and substrate thrown into the chamber. Regardless of design, the underlying technology remains the same.

For simplicity’s sake, we’re going to focus on residential applications. If you can turn your annual 220 pounds of food waste into usable cooking or heating fuel, I’ll consider that a win.

Biogas digesters aren’t complicated products. They’re designed to maximize fermentation similar to how a colon ferments food.

Typically, that means a digester begins with an air-tight chamber filled with water. The liquid environment creates an anaerobic (oxygen-free) ecosystem that methanogenic microorganisms require to survive.

For residential systems, there are typically four classes of microorganisms that you need to introduce to produce methane.

1. Hydrolytic microbes break down insoluble carbohydrates

2. Acidogenic bacteria turn sugars and amino acids into carbon dioxide, hydrogen, ammonia, and other organic acids.

3. Acetogenic bacteria turn organic acids into acetic acid, hydrogen, ammonia, and carbon dioxide.

4. Finally, the methanogens process these compounds into methane and carbon dioxide.

Again, you don’t need to know the science.

You can rest assured that when organic waste drops into the liquid-filled chamber, the biogas dream team gets to work producing your cooking gas.

Fuel production isn’t the only benefit from their activity, though.

As each microbe performs its duties, the organic material they’re working on dissolves into the surrounding fluid. The water becomes a nutrient-rich “bio-slurry”, which is a better-sounding word than the reality (sludge).

The bio-slurry is compost tea on steroids. Once your biogas chamber begins producing, you can harvest the liquid fertilizer every day. If you’re lucky enough to grow some of your own produce, that means you’re closing the loop between production and consumption.

Take a second to imagine it:

1. You’ll harvest your fruit or veg, preparing it with your biogas-powered stove (chef’s kiss).

2. You eat what you want while your scraps (and other “organic waste products”) return to the biogas digester.

3. The microbes feast to their utter delight, producing more cooking gas for your next meal.

4. Excess nutrients dissolved in the liquid are harvested from the chamber, fertilizing your plants for even more production the following year.

In the end, you get waste treatment, fertilizer, food, fuel, and neighborhood bragging rights all in one investment. It’s magic, really.

If you’re interested in purchasing a residential biogas system, this is the best company I’ve found.

Large-Scale Biogas

Again, the underlying process that produces biogas doesn’t change much between small and large applications.

I won’t dig into the nitty gritty, but I do want to highlight some existing large-scale projects that are actively producing fuel across the world.

A recent development on a Bosnian dairy farm turns their plentiful cow manure into 600 kilowatts of electricity every hour. That’s enough to power hundreds of homes at peak consumption by harnessing the power of decomposition.

In the U.S., there are over 360 commercial-scale facilities using biogas digesters. They range from dairy farms like the one in Bosnia to a Gatorade bottling facility using wastewater for power cogeneration.

One California cheese maker turns their byproducts into over 710 kW of electricity. Using 60 tons of daily waste from 1,500 cows, grass trimmings, and cheese whey, the plant churns out double its energy consumption. It feeds the remainder back to the grid, earning another income stream from grid operators.

Where to now?

I suspect we’re still early on the biogas growth curve. The basic technology is old (like old-old). But the rates of methane emissions escaping from landfills and the volumes of food we discard are quickly becoming focal points in the search for alternative energy sources. Capturing those emissions for fuel seems like low-hanging fruit.

I’m sitting in a powerless Austin, TX house as I write this, and there’s one glaringly obvious reason to invest in a biogas system for your backyard.

If you want reliability, you need redundancy. In biogas, you get a surplus fuel source that sustains itself on otherwise useless waste.

See you next week, fellow Earthlings.

— Permacultured

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