Net-Zero Peanut Wagons & the Perfect Chip: Optimizing Biomass Processing at Charm

Imagine this: your phone rings, it’s a local forest management service. They’ve just completed a wildfire prevention project high in the Rockies and they want to know if you’re willing and available to take hundreds of tonnes of biomass off their hands. “Of course.” 

This is by no means a rare call to receive at Charm Industrial. We’re scaling up our biomass processing to thousands of tonnes per month at our new Miniforge Site, turning residual biomass into small, consistent, pyrolyzer-ready chips that are then converted to carbon-rich bio-oil and permanently sequestered.   

Over the past year, we completely redesigned our approach to biomass processing. Our goal was to minimize our carbon footprint while maximizing our throughput. 

The journey to the “perfect chip” took us across the country to test wood chippers and loading systems; it required hundreds of engineering hours spent analyzing chipping yields and updating test plans for drying techniques; and it ushered in a new fleet of processing equipment. 

In total, we were able to improve our biomass processing efficiency (measured as the “accept rate” for processed biomass) from 46% to 85%+ while cutting our processing emissions in half. This is what it looks like on the front lines of scaling up carbon removal. 

Our MVB: Minimal Viable Biomass Processing

Charm is focused on two sources of biomass residues: corn stover and woody biomass from wildfire mitigation projects. Each year, forest management for ecological health and wildfire resilience results in tens of millions of tonnes of residual biomass.  In many cases, getting this biomass out of the forest is essential to reducing the build up of fuel that could lead to catastrophic wildfire. 

Some of these thinnings can be used for lumber or other wood products, but the remainder of the material needs a market.  Charm provides a solution for land managers looking to get rid of excess biomass, and by putting it to use, we can help reduce the costs of wildfire mitigation for our communities and the taxpayer.

To process this biomass, we need to turn non-merchantable logs into small, consistent chips that are ready to be converted to bio-oil in our pyrolyzers. This processing happens in three steps: chipping, sorting, and drying. 

First, chipping. We have been successfully operating a relatively small, unmodified chipper for the past year, and although it’s been a trusty rig, it doesn’t have the throughput capacity we need for our next stage of scale. 

After we chip, we need to sort. Our original setup consisted of a modest two by three-and-a-half foot screen to process wood chips, sorting them into one of three processing paths by size. 

Finally, chips need to be dried to remove moisture. Initially, the correctly sized material was sent into a dryer which relied on forced air and propane-fueled heat to dry the chips (if you’re thinking “using propane doesn’t sound great for climate impact,” agreed! …Read on.). This “minimal viable biomass processing” setup yielded around 46% efficiency, with sizable CO₂ emissions from propane, which lowered our net removals.

Image Caption: Our initial chipping & sorting processOur approach is always to start to operate and then iterate quickly, so as to maximize learnings. It was a huge step forward to set a workable baseline for operations, but we knew there were massive optimizations to be made across the processing line in efficiency, throughput and emissions reductions. 

Learning through Real-World Testing

We spent the following months evaluating various chipping and drying techniques. 

To optimize our chipping process, we assessed numerous different chippers and their capabilities to produce high-quality chips with better yields. Our primary focus was on reducing the life cycle assessment (LCA) impact by making use of more of the material we gather and by removing fossil fuels as a heat source for drying.

Image Caption: Our equipment testing brought us far-and-wideWe explored several drying techniques, aiming for a system that wouldn’t become a bottleneck in our operations. We built a small test stand and operated it for several hundred hours to learn about the drying behavior of wood chips and their interaction with the moisture content of ambient air. 

Meet the Beast: Biomass Processing 2.0 

With our learnings in hand, we were ready to overhaul our setup with entirely new equipment. 

Based on the recommendation of our biomass operations team we introduced a new horizontal grinder, capable of processing logs at a much higher throughput and with a much safer loading technique (First, Do No Harm). We’re able to load the machine’s powered infeed conveyor using any of the log handling tools onsite, and through an abundance of knife and outlet screen trials, we’ve been able to increase our yield of acceptably-sized chips from 46% to above 85%.

Image Caption: The horizontal grinder setupOur sorting equipment has also scaled up. Our new blue screen is eight times larger than the previous one, and will be able to keep up with the demand of the entire fleet of pyrolyzers forecasted for the year.

Image Caption: Maximizing our filtering & screeningOn the drying front, we’ve adopted the use of peanut wagons. Yes, peanut wagons – not to be confused with Nutmobile – are typically used in peanut processing and sourced straight from the peanut capital of the U.S., Georgia. Each wagon can hold about five tonnes of wet wood chips which dry down to two and a half tonnes of dry chips.

The wagons offer a modular solution that can be dispatched for on-site processing. To dry the cargo, wagons are attached to large, bounce house-inspired fans that exclusively rely on air (without propane or external heating) to dry the chips in batches. This allows for a much more carbon efficient – albeit slower – drying period. We are able to operate these fans on clean electricity, keeping our impact low with this new solution. 

Image Caption: Our peanut wagon filled with biomass hooked up to fans for dryingIn total, these optimizations have collectively cut the emissions of our biomass processing in half, which means more net carbon removed from the atmosphere.

The Work Ahead: Improved Efficiency and Next Steps

Looking ahead, we're already starting to pilot the next stage of development where we're utilizing recovered heat energy from the pyrolyzers to enable faster drying. This not only accelerates our drying process but also provides a valuable use for the heat generated by the pyrolyzers.

Thanks to our team's hard work, we’ve made impressive progress in our biomass processing line. We’re continuously pushing towards more sustainable and efficient solutions and taking inspiration from across the US–from peanut processing to forest management technologies–to do it.

Image Caption: The amazing biomass engineering team who made it all happen