Does Biochar hold water?

This is a post from Kelpie Wilson, who has a blog about biochar.  I dare you to subscribe to it!

John S
PDX OR

Biochar is just charcoal that is suitable for use in soil and other biological systems. I like to compost it first to fill it with nutrients and biology. After going through a barn, a compost pile, or an animal’s digestive tract, it becomes a humus-rich soil that is stable and resilient.

You would think that these characteristics alone would make biochar a hot ticket item for anyone concerned with gardening, farming, forestry, or landscaping, that is, anyone who grows plants. But unfortunately, biochar is not cheap and the biochar industry has had trouble finding viable markets. Biochar has to compete with many other kinds of soil amendments that growers already use and are familiar with. As a new product, biochar has to prove itself and as an amendment that takes time to show its value (often more than one growing season) that is difficult to do.

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In recent years, the main driver of biochar markets has been the ability of biochar to sequester stable carbon from the atmosphere. Stable biochar can stay in soil for hundreds to thousands of years. It is measurable (just weigh the biochar and determine its stable carbon content with a simple lab test) and low risk. Unlike tree planting where anything can happen to a tree (fire, disease, logging), biochar in soil tends to stay there.

A plethora of protocols for carbon removal credits using biochar has brought much needed capital into the biochar industry, but now that may be going away. One of the main buyers, Microsoft, has turned to the more high tech carbon removal systems like BECCS — Biomass Energy with Carbon Capture and Storage — to meet its climate mitigation objectives. This scheme involves capturing carbon dioxide gas and pumping it deep underground for storage. Unlike biochar, there are no co-benefits to this dubious practice, but it looks good on paper because it scales!

Bankers and industry always want scale because it props up the balance sheet, but what good is it to everyone else?

There are many ways to make biochar. Some involve energy production like the biomass power plant near me that makes electricity and biochar. But other ways are more low tech and done on site right where the biomass is. This is the issue with biomass (ie, life) — it is widely distributed across the planet. In order to capture it and utilize it, you need to spend a lot of energy gathering it up. Life is antithetical to “scale” as the bankers think of it.

The main thrust of my biochar work these days is to develop and teach techniques to make biochar on site where it is used to benefit the life that is there. We have a network called Biochar On Site and you can visit us and learn more about it. We meet up on the first Wednesday of the month online to discuss progress and learn from each other.

Many individual landowners and other dedicated groups like The Biochar Coalition are making biochar using tools like my Ring of Fire Biochar Kiln, often as volunteers, because they care about soils, nature, and the future. But if we want this to “scale” they need to be paid for their work. If carbon removal funding won’t do it, what will?

Obviously, society needs to value healthy soils and ecosystems far more than it presently does. But this kind of holistic view is anathema to finance. Banks can only focus on single factors like carbon. So, given this limitation, and given that the carbon driver of biochar investment seems to be receding, what can take its place?

Water.

Water is like oil - we totally take it for granted until it is not there. This year seems to be the year that we will not only experience the sudden choking off of 20 percent of the world’s oil supply, but also record-breaking drought across much of our farmland.

Over 60 percent of US cropland is in drought condition. In Nebraska where farmers are experiencing the most severe conditions in the nation, more than half of the acres planted this year are expected to be abandoned, with some farmers anticipating a complete loss of thousands of acres.

Many other countries are experiencing similar or worse conditions. Globally, droughts have been increasing for years, and all of the monitors predict that drying trends will increase. Greenhouse gas global warming is fingered as the culprit, but deforestation and land use change are a huge part of the problem.

This is where the small water cycle comes in. A new look at the interaction of atmospheric physics and vegetation cover is finding that soil moisture and evapotranspiration from plants together play a crucial role in moving water from the oceans inland to send rainwater deep into the interior of continents. The whole water story here is complicated, but fascinating. You can learn more at Biodiversity for a Living Planet, but the gist of it is based on two principles:

   Make your soil like a sponge that absorbs and holds water

   Keep soil covered with living plants.

In other words, restore natural living systems and the earth, climate, and water cycles will stabilize once again.

The day is not far off when the world can no longer ignore the water crisis and will be hungry for solutions. Dams, desalinization, and drip irrigation will only go so far. Hopefully, biochar will gain attention as a powerful tool for increasing and retaining soil moisture.

Biochar, after all, is a sponge. It holds water both by absorption, filling all of its micropores with water, and adsorption, electrostatic attraction holding water on the surfaces of the pores.

Biochar will hold water differently in different soils because water is also held in the pore spaces between soil and biochar particles. Biochar is most effective in free-draining sandy soils.


This is how biochar holds water.

You can easily test biochar water holding capacity for yourself. One way is to plant tomatoes in different pots with different amounts of biochar added to the soil. Let them grow to big plants and then stop watering them completely. See which ones wilt first.

Here’s another way:


Results of a slump test at a farm in Massachusetts on the same soils but different management. Soil was packed in a kitchen strainer and let to sit for 1 minute in water before being turned over on a board. The soil on the left is from a conventional vegetable farm that uses tillage and chemical fertilizers and herbicides. The soil in the middle is from a tobacco farm that uses tillage, chemical inputs, but also cover crops. The soil on the right is managed organically and not-tilled and has had compost and biochar added to it. Biochar and compost feed microbes in the soil. Those microbes secrete substances which hold soil particles together. When it rains, soil with good aggregate stability holds on to soil particles and nutrients better benefiting the farmer and protecting water quality. Photo by USDA NRCS.

Biochar can also prevent erosion from runoff where rain hits dry, hydrophobic soils and flows away, carrying soil with it. Biochar improves water infiltration and could be used to fix eroded gullies. Here is an interesting report on how simply packing a rutted trail with biochar can stop erosion in its tracks (literally - a mountain bike single track):

The potential for biochar to help restore soil moisture and bring rain is huge. Already, subsistence farmers and horticulturalists have discovered this property of biochar and are seeing economic returns in dryland areas. Broad acre farming could be next to find a positive ROI from using biochar for water conservation, especially in the most impacted areas like the San Joaquin Valley in California.

However, the use case that most concerns me is forests. Forest are key to cooling the climate and key drivers of the small water cycle that propagates rain across continental interiors. Forests are also highly threatened by drought and wildfire. I live in the WUI (Wildland Urban Interface) along with millions of others, especially here in the western United States — hence my focus on turning our brush piles into biochar.

As drought impacts our forests, soil moisture declines. This translates into lower live fuel moisture, so that green trees become more susceptible to ignition. The more forests that burn, the less forest cover, and the more soils dry. It’s a bad downward spiral that needs to be arrested. Biochar can help with that — hopefully for only a small marginal cost over what we are already doing.

Right now we are spending millions on thinning forests of flammable fuels and clearing firebreaks along roads to help control wildfires. Mostly this material is piled and burned for disposal. The burning destroys organic soil, leaving a scar of hydrophobic ground where erosion can start and nothing grows but weeds. With one simple intervention, we could add a huge amount of value to what we are doing already.

Here’s the trick: put the burn piles out with water and save the biochar. See my Biochar Burn Pile Guidelines for the details.

There are hundreds of thousands of burn piles sitting on thousands of acres in the West today, waiting for the right time to burn. I am on a mission to quantify the marginal additional cost of providing water to put these piles out and make biochar before it all turns to ash and incinerated soil.

I know the water is there. I listened to a podcast yesterday on The Hotshot Wakeup with Derrick Holdstock, owner and operator of Western Fire Resources. Derrick had a lot to say about the rewards and challenges of owning a private wildland firefighting company. These businesses are critical to our safety, but they often don’t get the support they need from government contracts.

One issue is not getting called out on fires when they have invested money in equipment, maintenance, personnel, and training. Derrick called for the agencies to spend more money on prevention rather than suppression so his crews could have year-round work.

One of his biggest equipment costs is for water tenders. About half of the water supplied on any wildfire incident comes from independent contractors like Derrick. Private contractors are sitting on large amounts of water delivery capacity that is woefully under-used some years. It would be smart and efficient to use that capacity for fire and drought prevention by making biochar in the woods.

We could avoid the soil destruction and excessive smoke emissions of pile incineration while gaining carbon sequestration, water retention, and soil health. All it will take is a little water at the right time in order to save a lot more water in the future. The people and resources to do the job are out there, ready and waiting. We just need to get them paid so they can work.

Please, if you want to learn more about practical biochar tips and tricks for growing your own food, or you are interested in stewardship biochar for restoring natural ecosystems and biodiversity, check out some of my links below: