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.

An SSM Jet-Flame Optimized “Open Fire”

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Last week we wrote about using the LEMS to tune up a stove, so it makes sense to share the actual results of a recent test series with you this week.

When ARC makes an Open Fire, we often use three bricks on end to hold up the pot. The bricks are 16cm high. It has been fascinating to experiment with the SSM Jet-Flame in the open fire to try and determine how fuel-efficient and clean burning the combination can be. Last month, we spent a couple of weeks changing one thing at a time and then completed nine 30-minute ISO high power tests on the close-to-optimized design.

Here are the test results:

test results chart

Description of the changes

  • We kept the pot height at 16cm above the top of the Jet-Flame.
  • Three rebar supports held up the pot replacing the heavier and bulkier bricks.
  • A short 6cm high by 18cm long FeCrAl fence kept the sticks on top of the combustion zone in the Jet-Flame.
  • A lightweight Winiarski 304 stainless steel “0.7 constant cross sectional area” stovetop increased the heat transfer efficiency from the hot flue gases into the pot.
  • Thermal efficiency was also improved with an 11cm high pot skirt creating a 6mm channel gap on the sides of the 26cm in diameter pot.
  • We learned that the sides of the open fire should be partially enclosed for best performance. A 5cm high opening at the lower portion of the sides of the open fire allowed fresh air to enter the combustion zone. 11cm of the upper portion of the sides of the Open Fire were enclosed with aluminum foil.
  • To make sure that there was no backdraft, a 7cm tall, 14cm wide and 7cm deep metal fuel tunnel was added on the outside of the sides of the partially enclosed Open Fire.

Photo of the experiment

Conclusion

It looks like a Rocket combustion chamber may not be needed to achieve Tier 4/5 results from an “Open Fire” when tested in a lab. A short fence that holds a single layer of sticks on top of the primary air jets seems to be as good.

Tuning A Stove With Real Time Data

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PM2.5, CO2, CO and other metrics measured by the LEMS are displayed in a real-time graph during testing.

When enough data is available in real time, it is not hard to make progress improving a stove. The LEMS emission hood provides real time, holistic feedback as the experimenter makes changes. Watching all of the measures simultaneously makes it possible to tune a stove like a car. The goal is to burn biomass at high, medium, and low power with Tier 4/5 levels for thermal efficiency and emissions of CO and PM2.5.

It is easier in a forced draft stove.

Watching the real time PM2.5 data on a screen while turning two knobs that control the velocity/volume of primary and secondary air jets going into a combustion chamber quickly establishes a close to optimal compromise resulting in the lowest emissions. The stove “tune-up” process includes making sure that the temperature of the gases touching the pot stay as hot as possible, keeping the thermal efficiency high. Maintaining high temperatures in the combustion chamber is important as well. At the same time, the CO2 (a proxy for firepower) needs to stay around 5kW (high power), 4kW (medium power) and 3kW (low power). Since burning wood does not make much CO, the CO should stay low. The Oxygen (O) sensors (air/fuel ratio) warn us if the available Oxygen is too low.

Establishing a close to optimal balance of PM2.5, temperatures, CO, CO2, O is easier when working on a stove with metered fuel like a TLUD or a pellet burning heating stove. Consistent metering reduces disturbances in the rate of reactions (how fast the solid wood turns into woodgas). A standardized test, such as ISO 19867, provides data on fuel use, time to boil, thermal efficiency, firepower, emissions rates, etc.

After the real time balances look good, we use the more accurate pump and filter PM2.5 system with enough repetitions to establish statistical confidence. It usually takes two to four weeks to tune up a stove. After tuning up several similar stoves, the data can coalesce into time saving design principles. Data derived design principles are more likely to be predictive.

Dr. Kirk Smith and The Breathing Space Project

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Dr. Kirk Smith, a hero

ARC worked closely with Dr. Kirk Smith (1947-2020) when we helped to include emissions in the Water Boiling Test, used to evaluate biomass cookstove performance, for the Shell Foundation. We included the first “Tiers of Performance” with a simple approach that divided stoves into two categories: improved and unimproved. It was great to know Kirk and I admired him tremendously.

Kirk was a professor at the University of California at Berkeley and was, in my opinion, the most effective advocate for the billions of people afflicted by breathing smoke. Kirk and ARC continued to work together during the Breathing Space project in India. Here is a video that ARC helped to produce in 2009, which describes the project. 

The goal of Breathing Space was to introduce the Rocket stove into India. We hoped that the Rocket stove, after being re-designed by women in 18 villages, would “go viral” and protect health. Eventually, Envirofit become the distributor and project manager. Envirofit and the Shell Foundation worked together to bring Rocket stoves into markets worldwide.

In 2011, Kirk Smith announced that switching to LPG seemed more likely to protect health. By 2017, Envirofit was including LPG and gas stoves in their catalog of options. Trying to create and disseminate truly clean burning biomass stoves had proven to be difficult and a more successful, wide scale intervention was needed. Although people liked it, the combustion efficiency of the Rocket stove just was not good enough. The Justa stove with chimney (with Rocket combustion chamber) that Kirk tested in Guatemala leaked, and when many stoves were in use the outside air became smoky. Maybe gas stoves, even though the fuel is not renewable, had a better chance to succeed?  

What would Kirk Smith recommend in 2022?

Can market driven biomass stoves (with hay boxes, solar stoves, pot skirts, SuperPots, Jet-Flames, etc?) successfully address health and climate change? Maybe we should keep working and find out?

I think that Kirk would not object.

Illustration of how an electrostatic precipitator works

Post Combustion Reduction of PM2.5

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Illustration of how an electrostatic precipitator works
Electrostatic Precipitation: Smoke particles are negatively charged and attracted to positively charged metal plates that are automatically cleaned.

Both automobiles and the biomass industry rely on improving combustion efficiency and post combustion reduction of PM2.5 to achieve “clean burning.” It’s really hard to rely on the combustion chamber to burn up enough of the harmful smoke to protect health, especially in large scale applications. Of course, all efforts should be made to be as efficient as possible. The goal is to burn up everything! In cookstoves, with limited space and a pressing need to be affordable, the problem becomes more acute.

Biomass heating stoves are larger and can cost a lot more than cookstoves. Industrial technologies are even less constrained. For decades, home heaters have tried catalysts to reduce emissions. Factories have used a wider array of technologies including filtration, catalysts, and electrostatic precipitation. Chapter 8 in “Clean Burning Biomass Cookstoves, 2nd edition, 2021” includes explanations of these technologies. 

Generally, filtration can work very well to capture dust and smoke with reported efficiencies of up to 99% (Frisky, et al., 2001). Catalytic converters are placed into the hot exhaust path where temperatures are hot enough (above 426°C). They work well with CO (30% to 95%) but not so well to remove PM2.5 (30% to 40%) (Hukkanen, et al., 2012). The Swiss electrostatic precipitator (ESP) called the OekoTube has been measured to reduce PM2.5 by 80.2% to 97.7% (Brunner, et al., 2018). However, as in industrial uses, routine cleaning is necessary to remove creosote and other coatings that interfere with proper function. Unlike filters and catalytic converters, the low wattage ESP does not reduce the draft in the stove, which could be potentially advantageous. 

ARC has been experimenting with post combustion of PM2.5 since 2017 as a result of the EPA SBIR funded work to create a clean burning biomass heating stove. We believe that if ESP is to be useful, automatic self-cleaning must be included, as in some industrial products. The hope is to invent super clean combustion but it’s great that post combustion approaches already exist. On the other hand, forced draft mixing, which is relied upon for combustion efficiency in industry, is largely missing in both cookstoves and residential biomass heaters. Perhaps its addition will be sufficient to reach the goals of protecting health and carbon neutral fuel use with renewably harvested biomass?

Mass, Insulation and Thermal Efficiency

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Kuniokoa Stove, original top replaced with cast iron top.

It is more likely that close to 50% thermal efficiency will be achieved with a biomass burning stove when:

  • Small sticks are burned that produce tall, hot flames while using the least amount of wood.
  • A 30cm in diameter aluminum pot is used with a 14cm high pot skirt that creates a 6mm channel gap.
  • The stove top (with 6mm pot supports) weighs as little as possible. The narrow channel gaps in the stove top effectively deliver wasted heat from the hot gases into the stove top while increasing beneficial convective heat transfer into the pot, so less mass to hold the heat is better.
  • A grate helps the sticks to make tall, hot flames and reduces the made charcoal.

Starting with all of the above, we tested various Rocket stove combinations to try to determine the effect of mass in the combustion chamber. The Kuniokoa Rocket stove is the lightest Rocket stove in our museum – it is made from sheet metal without insulation. (A refractory metal combustion chamber lasts longer when uninsulated.) When tested at high power (4,645 watts) the thermal efficiency was 51.7%, PM2.5 was Tier 2, and CO was Tier 3. Thermal efficiency dropped to 46.1% when we exchanged the Kuniokoa sheet metal stove top (0.31 kilo) with a cast iron version (2.36 kilo).

A similar Shengzhou Stove Manufacturer (SSM) Rocket stove was tested with a refractory cement combustion chamber (2.7 kilo) surrounded with rock wool insulation. The stove top was made from lightweight 304 stainless steel. When tested at high power (4,816 watts) the thermal efficiency was 48.6%, PM2.5 was Tier 2, and CO was Tier 3. The refractory cement combustion chamber is heavier but it can be insulated because the material has a working temperature of 1,100°C.

When a SSM lighter refractory ceramic combustion chamber (1.2 kilo) was exchanged into the SSM Rocket stove with rock wool insulation and a lightweight 304 stainless steel stove top, the thermal efficiency (at 4,709 watts) rose to 51.4%, with Tier 2 for PM2.5 and Tier 3 for CO.

  • It may be that insulating a one kilo combustion chamber in a Rocket stove offsets the disadvantage of the higher mass when compared to uninsulated sheet metal.
  • In these tests, adding another kilo to the insulated combustion chamber in the SSM Rocket stove lowered thermal efficiency from 51% to 46%.
  • When the mass of the stove top was increased from 0.3 to 2.3 kilos, thermal efficiency dropped by about 5%.

Justa, Dos por Tres, Patsari Stoves!

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Dos por Tres Stove with Chimney, photo courtesy of Proyecto Mirador

During an ETHOS panel discussion on Cooking, Health, and Climate, it was great to see that the Justa stove with chimney protected health so well. Chimneys are mandated by law in the USA/Europe/China and many other countries. When Mahatma Gandhi returned to India from England he introduced chimneys as a logical upgrade of kitchens.

The WHO (2018) listed five prescriptions to protect health:

  1.  Use only clean household energy when available 
  2. While waiting for gas, use technologies like low-emission biomass cook stoves
  3. Minimize the time children spend around smoky fires
  4. Increase ventilation
  5. Install a chimney

Functional chimneys are the historical first step to protect health.  It’s so pleasant to sit and chat in the clean kitchen when a Justa, Dos por Tres, or Patsari stove is being used! Following up with improved combustion efficiency helps to protect climate and outdoor air quality.

A Justa Stove with chimney, photo courtesy of Stove Team International

ETHOS is Great!

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Yesterday morning I was on an ETHOS panel discussing stoves, health and climate change. I loved the discussion and was filled with hope that facing the end of the fossil fuel era might catalyze better use of resources.  Living sustainably has been a dream of mine since I was 15 years old in 1967. Like many people I have been living with this dream for many years in a world that has not been committed to renewable energy.

Aprovecho (started in 1976) has tried to create better understandings of farming, forestry, and appropriate technology (focusing on biomass stoves), and helped me to investigate fire. Working with Dr. Larry Winiarski was a blessing in many ways, especially by showing me the utility of the scientific method.

It was great to be able to direct folks at ETHOS to our 2020 revised book “Clean Burning Biomass Cookstoves” that contains most everything that we’ve learned since the publication in 2015. Download here: Clean Burning Biomass Cookstoves, 2nd Edition, 2021. These newsletters are another “closer to real time” update.

The ETHOS Conference continues online through Friday (Jan. 28). You can see the agenda, watch pre-recorded presentations and register to attend the live seminars/discussions at ETHOS 2022. I think you will find it well worth your while!

-All best, Dean Still, Research Director