Biochar and Hot Compost: Closed-Loop Fertilizing My Garden

The Inspiration: Michael F. Smith's Earth Lodge Revolution

I was recently inspired by watching a documentary that featured Regenitech founder Michael F. Smith and his incredible journey through the creation, destruction, and rebirth of his Earth Lodge. It's a terrific technology that operates as a completely closed-loop system, using biochar, algae, and the byproducts of both to create algae-bio-activated charcoal for plants. I was deeply moved by his story, especially learning that his first Earth Lodge creation burned down in a fire—what could have been a devastating setback became the catalyst for years of innovation and refinement. He has since redeveloped and advanced his technology, now making it available for both commercial and personal use.

Michael's algae-biochar integration system fascinated me, but I don't have extensive background in growing or using algae. So I decided to start my own experiments using materials that are freely available around me: waste wood and free mushroom compost from a local company in Crossfield. This approach allows me to explore the principles of closed-loop soil building while working with what nature provides in my immediate environment.

The Science Behind My Biochar Adventures

What makes biochar so magical? Biochar significantly boosts microbial abundance and C- and N-cycling functions, increasing the potential nitrification rate by 40.8% while reducing cumulative N2O by 12.7%. When I inoculate my homemade biochar with hot compost containing horse manure and hay, I'm essentially creating a microbial paradise.

Research shows that biochar amendment increases the relative abundances of beneficial bacteria known for their ability to fix nitrogen, solubilize phosphorus, or reduce iron and sulfur. These bacteria are the unsung heroes that contribute to the "biochar effect" in the rhizosphere—the magical zone around plant roots where all the nutrient cycling happens.

The process I use involves letting the biochar-compost mixture sit and keeping it moist, creating the perfect environment for mycorrhizal networks to establish. Then I add a hay mulch layer to retain moisture and suppress weeds. It's worked remarkably well—almost too well in some cases!

My Garden Laboratory: Current Experiments in Action

Here's what I've got brewing in my backyard soil science lab:

The Hot Compost Aluminum Beds: Unexpected Champions

I have two aluminum raised beds that have become my star performers. Each contains about 10 inches of hot compost topped with 20 inches of hay—a simple but effective lasagna layering system. Within these beds, I'm growing my "Three Sisters plus one": potatoes, corn, beans, and squash.

Initially, I was worried about these beds because the compost got quite hot, and the interface between compost and hay developed a moldy layer during a week of heavy rain. But here's where nature surprised me: this bed has been the only one to successfully germinate my bean and squash seeds!

The reason? Biochar's ability to increase water holding capacity in soils can also help make farms more resilient to drought and less reliant on irrigation. My hot compost created a microclimate that maintained 15-20°C of warmth throughout those rainy days. This is impressive because squash normally doesn't germinate until late June in my area, so this system could potentially extend my growing season and protect against late frosts during the tricky May-June transition period.

Cedar Biochar Battle: The Side-by-Side Comparison

My most rigorous experiment involves two identical cedar raised beds—one with biochar, one without. Both contain three-month aged compost (no longer hot) and a four-inch layer of hay. I'm growing the same varieties in each: Hopi corn, beans, and tomatoes, keeping water and nutrient levels as consistent as possible.

Currently, the non-biochar bed is performing better, but I suspect this is because it receives slightly more sunlight, thus warming the soil more effectively. Research indicates that not all soils are well suited for biochar—well-drained sandy soils experience biochar benefits such as increased soil moisture retention, but moderately well-drained soils may not always respond as positively.

This experiment is teaching me that biochar must be carefully balanced with plant nutrients, as an imbalance can lead to the absorption and unavailability of applied nutrients. I suspect my biochar wasn't completely inoculated before application, which is a crucial step I'm learning to perfect.

The Microbial Magic: What's Really Happening Underground

When I mix biochar with hot compost, I'm essentially creating a five-star hotel for soil microorganisms. Biochar improves soil physical and biochemical properties and increases soil fertility and productivity—particularly over the long-term—increasing soil aggregation, water retention, pH, and microbial activities.

The process works like this: biochar derived at lower pyrolysis temperatures can better improve dehydrogenase and acid phosphatase and thus nutrient retention. My homemade biochar, created through simple wood burning, operates at these lower temperatures, making it ideal for nutrient retention.

The hay mulch layer serves multiple purposes—it keeps the biochar-compost mixture moist, provides carbon for the soil food web, and suppresses weeds. However, I've discovered that while it excellently prevents weed growth, it can also keep soil temperatures quite cool, which sometimes interferes with seed germination.

Looking Ahead: The Aquaponics Adventure

Inspired by Michael's algae integration, I'm planning to incorporate aquaponics principles into my system. Fish waste acts as a natural fertilizer for crops, and the basic principle of aquaponics is to put waste to use. I'm excited about adding fish to my rain barrels to create nutrient-rich water for irrigation.

Aquaponics uses about 2% of the water required by conventional irrigation methods for the same vegetable production, making it an incredibly efficient system. The fish waste provides ammonia-laden water that is processed by helpful bacteria such as Nitrosomonas and Nitrobacter, which convert ammonia into nitrite and then nitrate—both excellent plant fertilizers.

The key is ensuring humane conditions for the fish while maximizing the nutrient benefits for my plants. I'm researching cold-hardy fish species that could thrive in outdoor rain barrels through Alberta's growing season.