Closing the Loop – Biochar as Carbon Negative Technology

by Dan Hettinger, Living Web Farms Biochar Production Manager

The increase in annual global carbon emissions has stalled in recent years despite strong global economic growth, in effect, economic growth is no longer coupled to increased carbon emissions.  In 2015, most of the world agreed that we can limit climate change to 2 degree C rise.

This is all great news, for everyone, especially those who are most impacted by climate change.  However, some say that the 2C goal is unattainable without the use of technologies that actively remove carbon from the atmosphere.

Biochar production has been recognized as one of these carbon negative technologies.

Biochar is biomass, carbonized through a process called pyrolysis, that renders its labile carbon in a more stable form.  When added to soils, this inert, recalcitrant carbon is resistant to decay, and has the potential to sequester carbon much longer, potentially for thousands of years.  For those that have followed our work here at Living Web Farms, you know that with the help of our friends at Chargow,LLC we’ve talked about this before.

We all know plants take in carbon dioxide in a process called photosynthesis, and this carbon is released when these plants are burned.  What might not be as apparent is how most of this stored carbon in dead material is slowly released back into the atmosphere through eventual decay.  This is where the pyrolysis process comes in.  Instead of being piled up and burned, or left in the field to rot, waste plant material is diverted into an oxygen limited chamber, called a retort. Here, through the application of heat, complex molecules present in the biomass are broken down either into gasses that can be easily condensed as wood vinegar, tar and bio-oil, or non-condensable gasses that be stored or burned for heat or electricity.  Leftover from this process is a high quality lump charcoal that we call biochar when it’s incorporated into soils.

Collecting “slab wood” at a local sawmill. This stuff has little commercial value. Some mills sell it as wood chips, others pile it up and burn it.

 

For years now we’ve been making biochar in batches with wood waste from local mills.

We use a 14’ diesel flatbed for pickup and local shipments, an LP forklift, our share of gasoline small engines and a fair amount of electricity running various blowers and pumps:  these are carbon heavy tasks we do on a regular basis.  In light of this, we wanted to know if we could still claim to be carbon negative. Determining a carbon footprint requires a detailed look at the throughput of the facility – what goes in and comes out – including all the hidden sources of carbon usage (down to the RTV silicone we use for gaskets).  After modifying their models, This group, from the front lines of the hemp industry was able to do a carbon life cycle analysis for our biochar facility.

A site visit in January of this year revealed:

 

This means, at present, we sequester about 4 lbs carbon dioxide equivalent for every 2.2 lbs of finished biochar.  Our average yield of 7 400 lb batches of biochar/week means we sequester 5,189lbs of carbon every week.  To put this in perspective, I drive nearly 60 miles round trip (I know) just to get to work. The EPA tells us the average car emits 441 grams CO2/mile, so at 60 miles, I emit about 58 lbs carbon just getting to work (about 5% of our total carbon sequestered).  I’ll mention that electric cars typically emit about ⅔ less carbon emissions.  For someone like me, that commutes just in the range of most typical electric cars, this is an increasingly obvious choice.

Processed biochar is stored in large woven polypropylene bags like this before shipment to our affiliate farms. These bags are made in India – literally the other side of the world. Since learning of the carbon impact of shipping these, we’ve switched to a different style bag that can be easily reused in the field up to 5 times.

 

Let’s look at our operation in a little more detail:

 

  • Transportation is a huge part of our carbon emittance.  In the short term, we’ll be switching our diesel trucks to run on 20% biodiesel.
  • Even though our inputs are nearly 50% hardwood, their value in sequestration is significantly higher.  As producers, we can prioritize collecting hardwood waste when possible.
  • Our electricity inputs are not negligible.  We can shave electricity costs through efficiency measures, then further explore our options with generating our own via solar, syngas generators, stirling, ethanol or small scale steam.

Carbon Negative is absolutely possible with biochar.  It’s worth noting there are other carbon negative technologies, some more accessible than others. Though simple carbon negative technologies and carbon smart farming exist, these practices can’t be seen as a license to pollute.

For carbon negative production it’s likely that small scale producers have an edge here.   Farmers and enthusiastic homesteaders have a real opportunity to go carbon negative through the use of simple ‘backyard biochar’ technologies like the TLUD, Tin-man and Kontiki kiln.  These systems can use common landscape wastes generated on your own property: limbs, chips, sticks, as feedstocks for high quality DIY biochar.  Transportation, processing, electrical, and application inputs are all null with these systems when biochar is produced from feedstock generated and then applied on your property

To me, most fascinating of all is the role of biochar applied in the soils.  In soils, biochar has a cascading effect where microbes (carbon) take up residence in its micropores, cycling more nutrients, processing organic matter (carbon) and facilitating the growth of mycorrhizal fungi (more carbon!)  Improved soil fertility means more trees survive, ecosystems are healthier and we’re more than one step closer to that 2C goal.