I first became interested in biochar 25 years ago when a professor told me about the discovery of dark earth soils in the Amazon. Two things stood out: first, these soils were incredibly fertile compared with surrounding areas and, second, they were loaded with carbonized organic matter similar to weathered charcoal. This led many of us to think that we could replicate these soils by adding pyrolized organic matter, called biochar, to farmland and gardens.
When we started Arthur’s Point Farm, we began making biochar in a retort kiln and amending our soil with it. We were eager to learn more about how well it really worked, so we launched a four-year research project funded by the USDA’s Sustainable Agriculture Research and Education (SARE) program. Our findings are reported on the SARE website. We also created a Biochar Web Series and an accompanying documentary film, Biochar for Farmers, to help distill and disseminate what we’ve learned about biochar.
Biochar is often presented as a breakthrough agricultural input - a tool that can improve soil health, increase yields, build resilience, and store carbon for centuries. Across conferences, marketing materials, and online discussions, it’s often described as a universal, regenerative agricultural solution.
The scientific literature paints a more complicated picture.
Research on biochar has expanded rapidly over the past two decades, yet the results remain highly variable. Some studies report improvements in crop growth, nutrient retention, or water-holding capacity. Others show minimal effects or no measurable benefit at all. In some cases, negative outcomes have also been observed.
What becomes clear after reviewing the literature is that biochar does not behave consistently across soils, climates, crops, or farming systems. Whether it helps and whether it’s worth the cost and labor depends heavily on context.
Our purpose is to help farmers and gardeners cut through the hype and get to the bottom line of what the science actually tells us about biochar.
What Biochar Actually Is
Biochar is a carbon-rich material produced by heating biomass in a low-oxygen environment through a process called pyrolysis. Feedstocks may include wood, crop residues, nutshells, manure, forestry waste, or even bone.
Different feedstocks and process temperatures produce varied types of biochar. For example, a low-temperature biochar made from manure behaves differently than a high-temperature hardwood biochar. Some materials contain more ash and nutrients. Others are more porous or chemically stable. Some may raise soil pH significantly, while others have relatively little effect.
Learn More - What Is Biochar? Pyrolysis, Soil Effects & Farm Use
Why Farmers and Climate Activists Became Interested
Interest in biochar grew largely from two ideas.
The first was the discovery of Terra Preta soils in the Amazon — dark, carbon-rich soils associated with historical Indigenous land management. These soils contain charcoal and often exhibit unusually high fertility compared to surrounding tropical soils.
The second was the possibility that biochar could function as a climate tool by stabilizing carbon in soils for long periods of time. Because pyrolysis converts plant biomass into a more decomposition-resistant form of carbon, biochar has been proposed as a way to store atmospheric carbon captured by plants.
Over time, broader claims emerged: increased microbial activity, drought resilience, reduced fertilizer use, improved yields, and even ecosystem restoration.
Some of these outcomes have been reported under specific conditions. But the literature does not support the idea that biochar reliably produces these results across all agricultural systems.
Learn More - Terra Preta Soils: What They Do and Don’t Prove
Where Biochar May Help
The strongest evidence for biochar benefits tends to occur where a clear soil limitation already exists.
Examples include:
- Sandy or coarse soils with poor water retention
- Acidic soils where liming effects may help
- Highly weathered tropical soils with low nutrient-holding capacity
- Degraded soils with very low organic carbon
In these situations, biochar may improve water availability, influence pH, or help retain nutrients that would otherwise leach away.
Learn More - Does Biochar Increase Yield? The Evidence Gap Explained
But even here, results vary depending on:
- application rate
- feedstock
- pyrolysis temperature
- climate
- crop type
- whether fertilizer or compost are also applied
Importantly, many reported benefits may result less from unique biological properties of biochar itself and more from conventional soil chemistry effects — particularly changes in pH, nutrient additions from ash, or the interaction of biochar with compost and fertilizers.
Learn More - Biochar Feedstock & Pyrolysis Temperature: Why It Matters
Why Field Results Often Differ From Greenhouse Studies
One reason biochar can appear more promising online than in practice is that many studies are conducted under highly controlled conditions.
Greenhouse and pot experiments often:
- use finely ground biochar
- apply high rates
- minimize environmental variability
- run for short durations
- use optimized irrigation and fertility
Real farms are more complicated.
Field conditions introduce weather variability, soil heterogeneity, microbial competition, equipment limitations, and economic realities that frequently reduce measurable effects. Many positive greenhouse outcomes become weaker or inconsistent when tested at field scale.
This does not mean biochar doesn't work in the real world. It means farmers should be cautious about extrapolating laboratory outcomes directly to commercial agriculture. More realistic field trials under typical real world conditions are needed to clarify expected benefits, application rates, and costs.
Compost Often Matters More
One of the most consistent themes in the literature is that biochar tends to perform better when combined with compost, manure, or fertilizer.
This has led some researchers to suggest that the biological stimulation often attributed to biochar may actually result from nutrient additions and organic matter inputs rather than from biochar alone. Compost supplies microbial activity and nutrients; biochar may sometimes function more as a physical substrate or stabilizing material within that system.
For many farms, improving compost management, cover cropping, reduced tillage, perennial plantings, or organic matter cycling may provide more consistent returns than adding biochar.
Learn More - Biochar + Compost + Fertilizer: What Research Supports
The Economics Matter
Even when biochar shows positive effects, economics remain a major consideration.
Commercial biochar can be expensive to purchase, transport, spread, and incorporate. On-farm production requires labor, equipment, feedstock availability, and attention to emissions and safety concerns.
In our own field research and farm experience, producing high-quality biochar while simultaneously managing the many demands of a working farm proved difficult and time-intensive.
This is especially important because many published studies apply biochar at rates that may not be economically realistic at commercial scale.
A useful question is not simply: “Does biochar improve yield?”
But rather: “Does biochar improve yield enough to justify the cost compared with other available practices?”
Biochar and Climate Change Mitigation
Biochar is often described as a carbon-negative technology because it can stabilize a portion of plant-derived carbon in soils.
Whether this is true depends on many specific variables of production and use. Biochar carbon can persist far longer than ordinary organic matter under many conditions. But estimates of permanence and additionality vary widely depending on feedstock, production conditions, soil environment, and land management.
The climate implications also depend heavily on:
- how the biomass is sourced
- what emissions occur during production
- whether fossil fuels are displaced
- how efficiently pyrolysis systems operate
- what would have happened to the biomass otherwise
As with agricultural performance, the climate story is more conditional and system-dependent than simplified summaries often suggest.
Learn More - Biochar as a Climate Solution: Carbon Storage & Lifecycle Reality
A Practical Approach for Farmers
The current scientific literature does not support biochar as a universal soil amendment.
But it also doesn't support dismissing it outright.
For farmers considering biochar, a cautious and diagnostic approach is probably the most reasonable path forward.
That means:
- identifying the actual soil constraint first
- evaluating whether biochar directly addresses that limitation
- comparing it against other available soil management strategies
- testing small areas before broad application
- monitoring outcomes over multiple seasons
In many situations, biochar may function best as one tool among many rather than as a standalone solution.
Learn More - Practical Biochar Guidance for Farmers: When It Makes Sense
Final Thoughts
Biochar remains an active area of research with legitimate scientific interest behind it.
Some farms may benefit from its use under specific conditions. But the evidence does not currently justify treating biochar as a universally transformative agricultural input.
The strongest lesson from the literature may be a simple one:
Soils are complex systems, and agricultural outcomes are rarely explained by a single amendment alone.
For farmers, careful observation, realistic expectations, and small-scale experimentation are likely more valuable than sweeping promises.
