Frequently Asked Questions
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Bio-oil and Biomass
Carbon Removal
Bio-oil and Biomass
What is bio-oil?
Bio-oil is a mixture of water, organic acids, aldehydes, ketones, sugars, phenols and many other organic compounds derived from the thermal breakdown of cellulose. Unlike crude oil, bio-oil cannot sustain a flame, bio-oil has much lower energy density, bio-oil is quite acidic in pH, etc. Bio-oil and crude oil are very different, names aside. Bio-oil is produced through a process called “fast pyrolysis” where biomass like corn stover, rice straw, timber slash, almond shells, etc. are heated up to about 500°C in a few seconds without burning. This process produces a liquid mixture called bio-oil and a solid mixture of ash (like in a fireplace). The ash is a useful potash fertilizer.
How safe is bio-oil?
Due to its high water content and low energy content, bio-oil generally won’t sustain a flame on its own. Bio-oil is typically classified under NFPA as Health 2, Fire 2, Instability 0. As a comparison, crude oil is more flammable (Health 1, Fire 4, Instability 0) and ammonia is a greater health hazard (Health 3, Fire 1, Instability 0). Both ammonia and crude oil are chemicals used at large scale today. It's important to take care and precautions for handling chemicals generally, and bio-oil is no different. Part of our patent-pending process includes modifying bio-oil into a more stable and safe material for handling and injection.
What types of biomass does Charm use?
We are focused initially on two waste residue biomass sources: corn stover and forest mechanical thinning. In the United States, roughly 100 million acres of corn is grown every year. On average that acreage produces about 400 million tonnes of corn stover, of which about 200 million tonnes can be sustainably removed from the field without negatively affecting soil health, nutrients, water retention, etc. On the forest side, throughout the Western US increased forest fires in recent years will need to be mitigated with mechanical thinning and controlled burns. Mechanical thinning will produce tens of millions of tons of waste biomass. This is a great opportunity to convert forest fire fuels into good for the climate in the form of carbon removals.
In an MIT Tech Review article on Charm, skepticism was expressed that Charm’s business model might not be “scalable over the long term if farmers already use and sell much of this material.” Our research indicates this is not a large concern for our business model nor the overall goal of the company to remove significant amounts of carbon emissions from the atmosphere. For example, the US Department of Energy has studied waste biomass availability and “concluded that the United States has the future potential to produce at least one billion dry tons of biomass resources (composed of agricultural, forestry, waste, and algal materials) on an annual basis without adversely affecting the environment.”
Charm is committed to performing carbon removals with the highest quality and integrity, and to that end will support independent evaluations, life cycle assessments, and protocol development of bio-oil sequestration and share results publicly as they become available.
How do you sustainably source biomass?
Every year, roughly 110 billion tons of CO₂ cycles out of the atmosphere via photosynthesis, and back in via respiration (e.g. rotting) and fires. Charm takes advantage of the CO₂ capture work that plants are already doing, by sourcing sustainable biomass as an input into our pyrolyzers. We believe total sustainable biomass sourcing is in the range of 5-20 billion tons of biomass per year (which roughly translates to 5-20 billion tons of potential CO₂ impact per year.)
There are many important considerations with biomass sourcing, we'll cover a few here.
Nutrient return to the field and forest is critical. In fact, the biochar+ash solid stream produced in our pyrolyzers is expected to not only return potash and similar nutrients to the soil, but actually increase the soil carbon content and soil health due to the large volumes of biochar produced and returned to the field. Depending on the biomass type, we may also need to leave some of the raw biomass in-place on the field or forest floor. For example, corn stover can only be harvested to ~50% without impacting the erosion effects of rainfall on bare earth.
Additionality of the biomass given alternative use cases is also important. Specifically, if the biomass would've been used to generate energy and displace fossil fuels, we can't use it. Surprisingly, a very small portion of biomass is used for energy today, because the economics are worse than solar, wind and other renewables.
Minimal transport of biomass is also important. Biomass is a fluffy material, and transport can easily mitigate positive effects through particulate, CO₂ and NOx emissions. This is one of the reasons we've designed the pyrolyzers to work as close to the field as possible (or even on the field).
Carbon Removal
How does Charm’s carbon removal process work?
We’ve developed a new, patented method for atmospheric carbon dioxide removal: convert biomass to bio-oil via fast pyrolysis, prepare the bio-oil for injection, transport it to an injection well, and inject it deep underground. In the USA, injection wells are permitted under the EPA Underground Injection Control program. In total, our process takes atmospheric CO₂, captures it in biomass, converts the biomass to a carbon-rich-energy-poor liquid, and injects it into rock formations that have stored crude oil and gas for hundreds of millions of years.
Is bio-oil sequestration stable long-term?
At a high level, we are injecting a carbon-rich liquid into the same rock formations that have stored crude oil and gas successfully for hundreds of millions of years.
More specifically, bio-oil is denser than the brine, oil and gas in these underground formations. After injection, the bio-oil sinks within the formation. Even better, the bio-oil has tendency to polymerize into a solid, and at the temperatures and pressures in these formations, our surface-level 3rd party lab experiments have found that bio-oil becomes a solid, locked in place, in days to weeks after injection.
This leads to dramatically better permanence guarantees than CO₂ injected into an EPA Class VI well. The primary concern with direct CO₂ sequestration is that CO₂ is less dense than water, and as a result, the CO₂ rises to the top of its deep underground injection layer and spreads out across the underside of the impermeable cap layer that contains the CO₂. As a result, careful geological measurements and modeling must be done to ensure that the geological formation storing the CO₂ is impermeable far away from the main injection site. By comparison, bio-oil's high density (sinking) and solidification (locking in place) give substantially stronger guarantees of long-term permanence.
Is it safe to inject bio-oil underground?
First, the EPA has developed strict requirements for the design and operation of underground injection wells. In particular, reservoir injection wells are required to be very deep underground, far below any potable aquifers, and are continuously monitored to ensure compliance with EPA guidelines. Hundreds of thousands of wells are used all over the US and broader world today for industrial waste disposal (Class I), oil & gas related operations (Class II), a variety of storage operations (Class V) and carbon dioxide geological sequestration (Class VI). Bio-oil fits the requirements for a number of different well types depending on the jurisdiction.
As one example, we've used Class V salt caverns originally created by oil and gas companies engaging in solution mining or gas storage. Now empty, these caverns can eventually become sinkholes, and so must be refilled with solid material. In these wells, we intentionally polymerize the bio-oil into a solid that will stabilize these caverns. This solid formation of the bio-oil in addition to the thick walls of the salt dome prevents leakage into groundwater aquifers, and is continuously monitored to ensure compliance.
While the majority of injection wells do not pose an induced seismicity hazard, high volume water injection wells associated with hydraulically fractured shale production, that penetrate an existing fault can cause increased seismic activity. As the volume of disposal water increases pressure on and within the fault plane, the forces holding the fault in place decrease; slippage occurs when driving stresses exceed those resisting. Charm’s methodology for bio-oil injection is less likely to trigger seismicity as the volumes we are injecting and the rate we are injecting at are significantly below those associated with induced seismicity events.
For more information, see:
What’s the carbon life cycle analysis?
Every ton of biomass contains roughly 1.65 tons CO₂. Fast pyrolysis of the biomass into bio-oil emits roughly 0.78 tons CO₂ per ton of biomass, with that energy and carbon coming directly from the biomass. Other emissions associated with production amount of 0.017 tons CO₂ per ton of biomass, transport of biomass and bio-oil amounts to 0.002 tons CO₂ per ton of biomass, and injection emits 0.002 tons CO₂ per ton of biomass. As a result, on a net lifecycle basis, 1 ton of biomass entering our process leads to roughly 0.85 tons of CO₂e net atmospheric carbon dioxide removal. Over time, we expect to substantially improve efficiencies in this life cycle. These numbers represent long-term expected averages, you can see detailed lifecycle analyses for each delivery on our ledger.
Does Charm have capacity for further carbon removal?
We are scaling up capacity as fast as we can to serve early customers like Stripe, Shopify, Microsoft, Square, Zendesk and more. For the latest delivery timetable and availability, reach out to sales@charmindustrial.com.
Is bio-oil sequestration additional?
In order for Charm’s bio-oil sequestration process to be “additional” we need to be confident that the biomass we’ve used was not destined for other fossil-fuel replacing activities. For all our biomass inputs, we vet that the biomass would have rotted or burned in the field or forest. Over time we'll increasingly make this vetting transparent.
Why is bio-oil sequestration considered a removal and not an avoidance offset?
Over 100 GtCO₂ is exchanged between the atmosphere and biosphere annually via photosynthesis, decomposition, and combustion. Through appropriate selection of biomass residue feedstocks that would otherwise rot or burn, the conversion of biomass to bio-oil and the permanent geological storage of the embodied carbon is a net removal from the atmosphere.
Leading scientists in the field of BECCS and Biomass Carbon Removal and Storage consider it to be a removal. See here.
Charm is literally refilling the fossil fuel reservoirs that we emptied into the atmosphere, the same way they were filled up eons ago.
Since plants grow constantly and remove more CO₂ from the atmosphere with each growth cycle, the process can clearly reduce atmospheric CO₂ in the long run, not just slow its rise. Therefore, bio-oil sequestration is a removal.
What other environmental impacts need to be considered?
Not already discussed above are emissions of particulate and NOx and the potential for increased road traffic.
For some crops, like nut shells, which are already processed at central facilities, we expect to decrease particulate, NOx and road traffic by condensing (and possibly injecting) bio-oil immediately on-site rather than grinding up the shells and applying them across broad areas.
For other crops, like corn stover, which are generally not processed centrally, we will slightly increase particulate, NOx, and road traffic by moving our pyrolyzers to the edge of the field or operating the pyrolyzers on the field. These emissions are considered as part of our environmental reviews and lifecycle analyses.
Why don’t you just bury the biomass?
Others are working on this method. Landfills are expensive to dig, the geology is critically important, and we don’t believe the capacity to be as scalable or as permanent as injecting carbon-containing liquid into deep geological storage. The conversion of biomass into bio-oil via pyrolysis results in a liquid form with a higher carbon density, and is more easily handled, transported, and injected into existing wells. Additionally, simply burying biomass may lead to anaerobic digestion of the biomass and the emission of methane, which is a far more potent greenhouse gas than CO₂.
Why not use the bio-oil as fuel? Burying it seems like a waste.
Bio-oil has been researched for decades as a potential fuel. However, bio-oil’s energy content is less than half that of crude oil because it’s already heavily oxygenated. It’s also more expensive to produce than crude oil, and has a nasty habit of solidifying over time in storage. As a result, it’s not an economically viable fuel today, by a wide margin. Many have tried, none have succeeded. However, bio-oil is very high in carbon, and that habit of solidifying is useful if you’re trying to store it forever. So, it’s not a great fuel but it’s a great fit for geological storage.