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land carbon sequestration


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The Problem: Too many people, too little food.

Global demand for food is projected to double between now and 2050, when the UN estimates that the world population will reach 9 billion.  The amount of arable land in the world is finite.  For 6000 years, Man has been effectively converting forests into desert, but now we have technologies that can restore depleted lands back to productivity. Agribusiness companies will need to harness these key aspects to produce more food more effectively. 

We cannot afford to leave depleted lands unutilized if they can be reformed. We face some of the greatest environmental challenges today, including sustainably feeding the world’s 
masses in the face of climate disruption.

The Climate Foundation is meeting this challenge by restoring degraded ecosystems on land and in oceans. Concurrent with restoring degraded ecosystems, the Climate Foundation projects help feed the world’s masses sustainably, sequester carbon and help mitigate climate change, address sanitation, and promote economic development and job creation.

A Solution: Biochar 

Biochar (biological charcoal) draws carbon from the atmosphere, providing a carbon sink on agricultural lands. Biochar is biologically unavailable, sequestering fixed carbon in the soil for centuries to millennia, providing a tool to absorb net carbon from the atmosphere. Biochar also lowers the need for fertizlier and slows down water runoff.

Each year, agriculture fixes 30 gigatons of carbon, but when the plants die, 30 gigatons of carbon return to the atmosphere, resulting in little net change. When Biochar is mixed with compost, soil and has plants growing in this combination, Biochar  recovers and stores a large fraction of  carbon in the ground, which makes  an ongoing and significant reduction in atmospheric GHG levels. Biochar also reduces the need for fertilizer and  raises agricultural productivity in marginal soils. And because Biochar acts like a sponge, it significantly reduces  runoff, (which helps streams, rivers and the oceans, and reduces the need for petrochemical fertilizers. 

Biochar Fueling Agriculture


Biochar can alter the soil in several ways, and biochar made at different temperatures (between 300-700C) has varying properties.

Plant uptake of fertilizers in East Africa is often only 50%, which is costly and inefficient for the farmers. Biochar as a substrate for nutrients could raise that efficiency. Current trials in Kenya are researching the effect of biochar on soil pathogens. Biochar can buffer the soils and make them more resistant against crop diseases. 

  • pH: Biochar can be used as a buffer for acidic soils, improving the pH and thus nutrient uptake for plants.

  • Water retention capacity: Biochar-altered soils can hold more water, saving plants from drought longer than normal soils.

  • Carbon content: Soil generally needs to contain at least 3% carbon to make fertilizer use efficiency high enough to recoup its initial investment. Soils in Kenya have little carbon in them; carbon in biochar remains in the soils for decades.

  • Adsorption of nutrients: Biochar as a substrate for nutrients can increase the fertilizer use efficiency. We’re researching the potential of adsorbing nutrients to the surface of biochar, for instance those harvested in the urine collection.

Converting Human Waste to BioChar on a Community Scale

Biochar can be made from agricultural waste and/or human waste. Since 2011, the Climate Foundation has developed biochar reactors for human solid waste (HSW) applications. The reactors were designed in the United States and built simultaneously in Connecticut and India. Working independently of the grid, they can process the solid waste of 2,000 people per day or up to 800 kg.  The following is a quick rundown of the Climate Foundation biochar reactor

Biochar Poster

(view larger version, 1.6 MB)

  • Dryer: Solid human waste enters the system through the hopper, into which containers are emptied. An auger transports the waste to the belt. The dryer system efficiently lowers the moisture content from ~75% to 30%. Hot air from the radiators is sucked through the waste by the vacuum created underneath the rotating belt, drying the waste at a relatively low temperature.

  • Carbonizer/Catalyst: The waste is charred and sanitized when it is heated to a temperature between 300-700 degrees in the absence of oxygen. An auger in the bottom of the firebox subdivides any ash clinker to prevent clogging. Two augers underneath the firebox transport biochar to the collection box. The waste is initially pyrolyzed, releasing half the carbon as syngas suitable as a free energy source while charring the remainder.  Above the carbonizer, a catalyst cleans the exhaust by oxidizing gases.

  • Heat Recapturing System (Heat Engine + Condensing heat exchanger): A key feature of the biochar reactor is the heat recapturing system. Heat from the carbonizer and catalyst passes through the Heat engine. The engine’s internal heat exchanger produces electrical energy to power the belt dryer and augers. After powering the Heat engine, the excess heat is led into the condensing heat exchanger, where it transfers heat into the dryer by condensing water vapor present in the exhaust stream from oxidation and from the 30% moisture of the input material.

Where Do We Go from Here?

Science has shown that biochar improves poor soil, reduces the quantities needed of  fertilizer and water and holds gigatons of carbon for hundreds to thousands of years.  

By restoring natural carbon cycles, we can restore food productivity on the Earth while concurrently balancing carbon. Once we reduce the carbon intensity of our own lifestyles, natural biogeochemical processes can take our civilization carbon negative using technologies comprising biochar to withdraw gigatons of carbon from the atmosphere for millennia.

To date, the team organized by Climate Foundation has built multiple biochar reactors. The second generation reactors are completed, functioning, site tested and ready to launch.