Chart comparing energy output of 1 acre of grain vs 1 acre woodlot

Ethanol or Direct Burning for Heating Applications?

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The direct burning of biomass seems to be dramatically more efficient compared to ethanol for applications such as home heating, cooking, heating water, or drying clothes. It makes sense that not having to create alcohol from biomass would save energy. When the use of natural gas is decreased (due to climate change), burning biomass for heating seems like a fuel-efficient option that could reduce the extra burdens on electricity. 

One of my favorite reference books is “The Energy Primer” published in 1974. It has comprehensive review articles on solar, wind, water, and biomass energy. The following chart comes from a great article on biomass written by Richard Merrill. It shows that when renewable biomass is combusted, the efficiencies are much higher compared to making alcohol from biomass and then burning it.

The very clean burning of biomass allows efficient heating applications.

Chart comparing energy output of 1 acre of grain vs 1 acre woodlot
Smokestacks belch out smoke, spelling out CO2 in a blue sky. A Euro symbol floats to the right.

A Recent History of the Rocket Stove: 2022

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Smokestacks belch out smoke, spelling out CO2 in a blue sky. A Euro symbol floats to the right.
Image by Petra Wessman via Flickr

How can smoke, extremely dangerous for health and climate change, be ignored in carbon credit equations? Carbon dioxide and methane are counted but not smoke. Carbon dioxide is reduced when heat transfer is improved resulting in less wood being burned. Wood doesn’t make appreciable amounts of methane. 

Because smoke is not counted to earn carbon credits, smoky stoves with good heat transfer efficiency make as much money as clean burning stoves even though the Black Carbon in smoke is something like 680 times worse than CO2 by weight for warming. Because smoke is not included in climate credit math, adding clean burning to biomass cook stoves usually has to be as inexpensive as possible.

We know that adding high pressure mixing to Rocket stoves dramatically reduces smoke. As of 2022, forced draft is required to achieve adequate amounts of mixing. Mixing requires high pressures that (so far) cannot be made with natural draft. We know how to improve the Rocket but are in the process of completing the transformation to clean burning.

Nice to know the solution!

Learning From The Field, Part 2

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The Field Informs the Lab

In Part 1, we gave examples of how field studies can provide unpleasantly surprising results. Rocket stoves were designed to make a little less smoke and use substantially less fuel. So when the rocket stove was field tested by USAID the inventor, Dr. Larry Winiarski, was not surprised that the stove still made smoke. But the ARC team was surprised that it was not a real improvement over the open fire.

In 2011 the goals for cookstoves published by the Department of Energy asked that a stove use 50% less fuel and make 90% less PM2.5 to protect health when used indoors. Now in 2022 stoves are also supposed to address climate change, which means emitting less PM2.5 and hopefully making less than 8% black carbon. Field tests show that we need to make more improvements to meet these specific goals.

How are these reductions achieved in the lab?

  1. Use a chimney to reduce in-home concentrations of CO and PM2.5.
  2. In lab tests, approximately 850°C gases need to flow in tight channel gaps around the pot(s) to reduce the fuel used to cook by about 50%.
  3. Molecular mixing at 850°C (0.2 second residence time) can achieve something like a 90% reduction of PM2.5 (requires forced draft in a Rocket stove).
  4. This mixing reduces greenhouse gas emissions by about the same amount.

Natural-draft and forced-draft TLUD stoves burning pellets and forced draft Jet-Flame stoves burning dry sticks without bark get close to these reductions in the lab. Unfortunately, they frequently do not yet meet these goals in the field.

The lab has to move into the field to learn if current technology can accomplish modern goals. Let’s go!

Next week in Part 3: sometimes field tests show success.

Shipping and Climate Change

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Balthazar Schulte, Lyttleton Harbor, New Zealand

I recently read a Time article that pointed out that shipping accounts for 2.2% of annual global greenhouse gas emissions. To put it in perspective the writer, Aryn Baker, suggests that if shipping was a country, it would be the sixth largest CO2 emitter in the world, on par with Germany.

In her reporting from last year’s COP26 (UN Climate Change Conference), she writes:

 “It doesn’t matter if we want iPhones that come from China, steaks from Brazil or to tow an iceberg to Glasgow; we all depend fundamentally on international shipping for everything that we do,” says Johannah Christensen, head of the Global Maritime Forum.

“This just underscores the importance of decarbonizing shipping.”

Some ferryboats have transitioned to battery power. For the 60,000 ocean going cargo ships transporting global goods, the most promising technology, says Christensen, is either hydrogen or synthetic fuels.

Making these fuels available sustains the globalization the world depends on for just about everything. In The Age of Aquarius, renewable fuels keep ships rolling on the high seas as we transition from grey to green. Check it out!

Natural Gas, Methane and Nitrogen Oxides

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I didn’t realize that natural gas is mostly methane which is about 84 times worse for climate change compared to CO2.

As reported in the recently published study “Methane and NOx Emissions from Natural Gas Stoves, Cooktops, and Ovens in Residential Homes,” methane leaks are bad news for both environmental and personal health. (Lebel, et al, Environ. Sci. Technol. 2022, 56, 4, 2529–2539)

Methane risks

The abstract in the Lebel article states:

  • Natural gas stoves in >40 million U.S. residences release methane (CH4) ─a potent greenhouse gas, through post-meter leaks and incomplete combustion.
  • Using a 20-year timeframe for methane, annual methane emissions from all gas stoves in U.S. homes have a climate impact comparable to the annual carbon dioxide emissions of 500,000 cars.
  • In addition to methane emissions, co-emitted health-damaging air pollutants such as nitrogen oxides (NOx) are released into home air and can trigger respiratory diseases.
  • Our data suggest that families who don’t use their range hoods or who have poor ventilation can surpass the one hour national standard of NO2 (100 ppb) within a few minutes of stove usage, particularly in smaller kitchens.

Climate Change: Replacing Natural Gas and Coal Burning in the USA

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Could biomass energy reduce the increased demand on electricity for home heating?

Could the clean burning of biomass make a greater percentage of electricity partially replacing coal and natural gas, powerful climate forcers?

Source: www.eia.gov/energyexplained/electricity/electricity-in-the-us

As seen above, renewable energy now makes 20% of the electricity generated in the USA.

Residential and commercial energy use makes up 13% of USA greenhouse emissions. Making electricity generates another 25%. (Total: 38%)

Source: www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions

Could carbon neutral biomass energy help to heat more homes and generate more electricity?

Using the emission hoods in our lab, we are investigating how to design (and manufacture) very clean burning pellet and log-burning heating stoves.

We’ll update progress here.