Idle Brainstorm: Biochar, greenhouse and aquaponics

I’ve previously published a much unpolished brainstorm regarding the viability of aquaponics in areas like my Shenandoah Valley that experience a hard freezing winter and how to make the prospect more viable. Previously, I brainstormed about tapping into geothermal energy by sinking the domed transparent greenhouse into the side of a south facing hill with the mass of the earth serving to help regulate temperatures. As always, the energy required to provide heat to keep the systems working negates any benefit in year round production…and then some.

Since publishing the aforementioned post, I’ve brainstormed enough additional tidbits that I believe warrant another post. In order for the fish to survive the winter, the aquaponics system needs to be heated. There are many biological processes that produce heat that could be used singularly or in tandem. Due to the living nature of these processes, if one goes down or the temperature drops too far, they will all fail which would be the greatest weakness in this system.


Yeast converting sugars to primarily alcohol and carbon dioxide is an exothermic reaction meaning it also releases heat as a byproduct of the reaction. If this process occurs in a closed greenhouse, the carbon dioxide will feed the plants via photosynthesis while the heat produced can extend the growing season. I have yet to determine how much sugar would be need to be fermented to have a noticeable effect, but it is an option worth considering. As fermentation is carried out by slightly fickle microbes, the temperature would have to remain above 55-60 degrees for this process to be viable.

Composting (Decomposition)

The same heat that gardeners everywhere encourage in their compost heaps in order to speed the process of decomposition could be harnessed within a greenhouse. That heat indicates that decomposition is also an exothermic process. In fact this same logic is applied to winter husbandry of livestock…at least in the sustainable agriculture world.

Manure packs are formed in the winter when animals are kept on deep bedding. In order to preserve all of the nutrients in the livestock waste, more carbon bedding is added as needed. As the pack grows and anaerobic decomposition begins, the heat produced is enough to keep animals comfortable. Pigs are even better suited to this process when natural instinct leads to  the front-end loader built into their noses to burrow, turning the pile and creating aerobic decomposition. With animals like horses with dry manure, this might even create a fire hazard as it gets so warm but the wet manure of pigs negates the threat. Chickens also create a hotter aerobic environment in their bedding when they scratch for spilt feed, or if the pack is on bare earth, when they scratch for worms. Polyface farms just down the valley from my own reports that worms are active through the winter with this method.

Even if manure is not the primary source of nitrogen in the compost, there are still plenty of sources of organic matter from both on and off the farm: grocery store produce waste, spent coffee grounds from the local shops, restaurant waste, fallen leaves, household waste, etc. Like fermentation, the living microbes responsible for decomposition require heat to remain active through the winter.


Biochar is simply charcoal. I assume the added prefix is to make it sound more appealing as a soil amendment, one of many calimed biological uses for farms. Where I stand on biochar…I’m not sure yet. I’ve been researching and trying to find reliable studies but remain unconvinced. The fact that one of the first commercial biochar production facilities was shut down in a Ponzi scheme investigation (Source: FBI) certainly did do any favors in convincing me of all the claims made.

Regardless, I’ve still considered making my own charcoal for outdoor cooking. Any claims made of biochar proven by future science would be a bonus. There are some waste products of the farm that I don’t want to compost. Cedar, walnut and tree of heaven all contain compounds that inhibit the growth of many plants thus I am weary of adding the scraps that cannot be turned into firewood to compost. Charcoal is a viable alternative. My apprehension regarding actively harvesting biomass or diverting biomass from other uses solely to produce biochar would be lessened if the heat produced was put to a secondary use.

Unlike the other two processes, making charcoal in the greenhouse would not done by a living organism. Thus it would likely have to be the primary source of active heat while the living processes provide supplemental heat.


Could a combination of geothermal, solar, fermentation, decomposition and charcoal production keep a greenhouse or aquaponics environment alive in the winter? I’m not sure without doing some intense math. If I ever get the time or resources to dispose on the project, I might just give it a shot!

Also, have you thought of any additional, low input heating sources I have not considered? If so, please share!

Garden, Side Projects

Subterranean Aquaponics? (Brainstorm Session)

Season extension is typically the first step market gardeners take to increase productivity. On my farm, the garden production will be kept simple for the first year but that doesn’t stop brainstorming future innovations.

Aquaponics has always fascinated me. Being a very low input system, the fish feed the plants and can in turn feed me or be processed into fish meal which is the most expensive part of the chicken ration. Chickens can also be directly integrated by using their litter to feed composting worms, which in turn can feed the fish. So if economics ever shifted that placed higher commercial value on tilapia than the chicken, the model can easily be scaled to place fish into the lead role the aquaponics model.

Unfortunately winters here in the Shenandoah Valley, and the rest of Virginia west of the tidewater region, can be harsh. Any economic gain from aquaponics is quickly negated by energy expenditure to provide heat to keep the fish healthy.

Recently, my friend Brauck shared some innovative gardening practices. Plans for a $300 Underground Greenhouse that produces year-round sent the wheels in my head into motion.

The gist of the plans are to dig wide trench 6-8 feet deep in a southern-exposed location, pile the removed earth on the north side of the trench, and seal the trench with transparent greenhouse plastic. A visual representation is pulled from the link above:

Using geothermal energy (thermal mass of the earth) to regulate temperatures while adding trapped solar energy give such potential to this design. Even in winter a tiny solar arrangement could supply power to pumps. If this arrangement provides a stable enough environment while reducing or eliminating energy needed for heat, aquaponics may move from fantasy to viable to profitable.