From ashes to action: Wildfire char holds a hidden climate solution

Wildfires leave behind loss and ruin – charred homes, scorched forests, communities upended. Yet even in those blackened remnants, Professor Pei Chiu sees an overlooked resource with climate potential. 

In his lab at the University of Delaware, Professor Chiu studies “char,” the carbon-rich residue produced when biomass burns without much oxygen. His team has probed both naturally produced wildfire char and its artificial cousin, biochar.

The researchers uncovered a surprising role of chars: they can help starve methane-producing microbes and tilt microbial communities toward pathways that generate far less climate damage.

Why wildfire char is everywhere

Char forms whenever organic matter is heated at high temperatures with limited oxygen. In nature, that’s wildfires; in industry, it’s pyrolysis, the controlled heating of leftover biomass such as wood chips, corn stalks, rice husks, and other agricultural residues. 

Commercial “biochar” is already used to improve soils, blend into compost, and filter stormwater.

Wildfire char, by contrast, is scattered by the ton across burned landscapes and gradually worked into soils by wind, rain, and roots.

Chars that behave like batteries

Several years ago, Chiu’s group noticed something striking: chars made by pyrolysis behaved like tiny rechargeable batteries. They could store and release electrons – a property the team calls electron storage capacity (ESC). 

That matters because microbes make a living moving electrons around. In oxygen-rich settings, they “breathe” oxygen to accept electrons as they break down sugars. In oxygen-poor places – think landfills, manure pits, waterlogged soils, rice paddies, wetlands, or the guts of anaerobic digesters – other organisms take over. 

Among the most consequential are methanogens, microbes that churn out methane, a heat-trapping gas roughly 85 times more potent than CO₂ over the short term and responsible for about a third of current warming.

Chiu’s team showed that char gives many common soil microbes an alternative “breath.” In essence, char can stand in for oxygen as an electron sink, letting beneficial microbes keep metabolizing without ceding the field to methanogens. When that happens, methane production drops.

What wildfires have to do with it

Wildfire char has been part of Earth’s carbon cycle for millions of years. That longevity led Chiu to a simple hypothesis: if char has been embedded in soils for eons, microbes likely evolved ways to use it. 

Across a range of chars – those born in wildfires and those made in kilns – the team measured substantial ESC, enough to change who thrives in oxygen-limited environments. 

How much “charge” are we talking about?

The numbers are eye-opening. In lab tests, a single gram of char – about a quarter teaspoon – could hold on the order of 10²¹ electrons. Scale that to real-world biomass and the potential grows fast. 

U.S. agriculture alone generates roughly 140 million dry tons of crop residues each year (with corn stover and wheat straw leading the way), while forestry adds 60–70 million dry tons more. 

Collectively, Chiu noted, chars represent an immense rechargeable, bioavailable reservoir of electrons – he likens it to a “trillion-trillion-trillion” (10³⁶) electrons injected into the global biogeochemical cycle annually.

Turning down methane – naturally

In controlled experiments, all wildfire chars and plant-based biochars tested suppressed methane formation. 

The mechanism is elegant: by giving char-“breathing” microbes a competitive edge, the material helps outcompete methanogens, which still produce more than 50% of global methane today. 

Unlike a chemical additive that’s used once and gone, char can be reused by microbes repeatedly, serving as a long-lived electron buffer in soils, sediments, and engineered systems.

Cleaner water, healthier soils

Steering electrons through char doesn’t only curb methane. The same microbial pathways can keep arsenic from mobilizing into drinking water or crops and can remove nitrate and perchlorate from stormwater and groundwater. 

That dovetails with biochar’s existing uses in filtration and soil health, suggesting one material can deliver multiple environmental services at once.

None of this minimizes the devastation of wildfires, which destroy ecosystems, businesses, and lives. But Chiu argues there’s value in learning from what’s left behind. 

Wildfire char’s electron-trading ability points to a sustainable lever for climate mitigation and pollution control – one built on microbes already common in nature and on carbon materials produced at massive scales, whether by accident (fires) or design (pyrolysis).

Why the urgency – and the hope

CO₂ rightly dominates climate discussions, but it lingers for 50 to 200 years. Methane is different: far stronger in the near term and with an atmospheric lifetime of about 12 years. That makes near-term methane cuts an unusually fast-acting climate lever. 

“If we can find ways to reduce methane, we could see the impact within our lifetimes,” said Professor Chiu.

That promise keeps his team pushing on the basic science: How exactly do microbes “breathe” a solid? How do different chars – from different fires, feedstocks, or kiln settings – shift ESC and microbial behavior? 

And how can this knowledge be scaled into landfill covers, livestock waste systems, wetlands restoration, or post-fire land management so that nature’s own electron economy helps dial down a powerful greenhouse gas?

Char, in other words, may be the rare wildfire remnant that points forward.

Study co-authors include doctoral student Jiwon Choi and former graduate student Danhui Xin (now at the Southern California Coastal Water Research Project).

The research is published in the journal Environmental Science & Technology.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–