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Carbon Capture: Solution Or Band-Aid? | Earth Wise

July 13, 2022 By EarthWise Leave a Comment

The idea of capturing the CO2 emissions from industry and locking them up is nothing new. It’s been going on for decades in some places. Norway’s state-owned oil company Equinor has been holing away a million tons of CO2 a year for a long time. But overall, CCS – carbon capture and storage – has had very limited use. As of last year, there were only about 30 large-scale projects in operation around the world, capturing only 0.1% of global emissions.

There is now growing interest in CCS and many new projects are underway. A combination of rising carbon prices in Europe, tax breaks for CCS in the US, national net-zero targets, and the increasing need to ramp down global emissions are all driving rising CCS activities.

While recent reports from the Intergovernmental Panel on Climate change still claim that it is possible to remain below 2 degrees Celsius of warming without using carbon capture, there is growing belief that it may be necessary given the present pace of the transition away from fossil fuels.

Two industries that together produce about 14% of global CO2 emissions are cement and steel. These are both industries for which it is difficult to eliminate emissions regardless of the energy sources used. CCS may be the best approach to reducing their emissions.

But there is considerable pushback against CCS. The concern is that CCS is primarily a way to delay decarbonization. It encourages various industries to continue to use fossil fuels instead of shifting away from them. Nonetheless, CCS no doubt has its place as part of the solution to climate change.

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Solution or Band-Aid? Carbon Capture Projects Are Moving Ahead

Photo, posted June 5, 2022, courtesy of Mark Dixon via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Sand From Mining Waste | Earth Wise

May 10, 2022 By EarthWise Leave a Comment

The natural resources people use the most are air and water. It may come as a surprise that in third place is sand. Sand is used to make glass, computer chips, toothpaste, cosmetics, food, wine, paper, paint, plastics, and more. It is estimated that 50 billion tons of sand are used each year.

Concrete is 10% cement, 15% water, and 75% sand. The concrete required to build a house takes on average 200 tons of sand, a hospital uses 3,000 tons, and a mile of a highway requires 15,000 tons.

One would think that there is no shortage of sand, but we are using it up faster than the planet can make it and the extraction of sand from seas, rivers, beaches, and quarries has negative impacts on the environment and surrounding communities. For example, removing sand leads to erosion in riverbanks, significantly increasing the risk of flooding in some places.

A potential strategy to reduce the impact of extracting sand to meet society’s growing need for is also a strategy for helping to reduce the production of mineral mining waste, which is the largest waste stream on the planet. Mining produces between 33 and 66 billion tons of waste material each year.

A new study by researchers in Switzerland and Australia looked at the potential for using mining waste as a source of so-called ore-sand. Sand-like material left over from mining operations could be used for many current applications for sand. Separating and repurposing these materials before they are added to the waste stream would not only reduce the volume of waste being generated by mining operations but would also create a responsible new source of sand.

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Solution to world’s largest waste stream: Make sand

Photo, posted October 22, 2005, courtesy of Alan via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Wastewater As A Freshwater Source | Earth Wise

September 27, 2021 By EarthWise Leave a Comment

Water covers three-quarters of our planet, but freshwater – the water we drink, bathe in, and irrigate crops with – comprises only 3% of the world’s water and much of that is frozen in glaciers or otherwise unavailable. Nearly 3 billion people suffer from water scarcity for at least some of the year.

Natural freshwater sources – lakes, rivers, and groundwater – are under stress from the effects of climate change and from the increasing demands of city populations. The wastewater treatment plants in large cities represent a significant potential water source provided that sustainable and economical technologies to produce it can be developed.

Researchers at Lehigh University in Pennsylvania have patented an innovative ion exchange desalination process that is a legitimate candidate to transform wastewater into usable water.

Existing large-scale desalination systems make use of semipermeable reverse osmosis membranes that require an energy source to run the system. The Lehigh process, which they call HIX-Desal, harnesses the unique chemistry of carbon dioxide to take the place of the energy used in reverse osmosis systems.

Tests of the new system show that the salinity of treated wastewater can be reduced by more than 60% by the HIX-Desal process without requiring any reverse osmosis. At an Allentown, Pennsylvania water treatment plant where the system was tested, the researchers estimated that using the system could save about a million kWh per day in electricity usage, enough energy to power 94 homes for a year.

With this system, waste carbon dioxide from landfills or turbine exhaust can be used to desalinate municipal wastewater. It could be the basis of a circular economy.

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Desalination tech uses CO2 to tap into municipal wastewater as alternative freshwater source

Photo, posted November 28, 2020, courtesy of Richard Ricciardi via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Snakes Near A Plane | Earth Wise

September 15, 2021 By EarthWise Leave a Comment

San Francisco International Airport is the seventh-busiest airport in the United States. In a typical year, approximately 55 million people pass through SFO on their way to destinations throughout North America and beyond.

At some point during their journey to or from the terminals at SFO, each one of those people will pass by a seemingly unremarkable 180-acre parcel of land. Surrounded by highways and train tracks, the soggy and overgrown vacant lot isn’t just home to rows of power lines. It’s also home to the world’s largest population of the beautiful and highly endangered San Francisco garter snake.

According to a recent study conducted by the U.S. Geological Survey, there are approximately 1,300 San Francisco garter snakes at SFO’s West of Bayshore property – the greatest concentration of these snakes ever recorded.

Conservationists have long known that the San Francisco garter snake was in trouble. In fact, it landed on the U.S. Fish and Wildlife Service’s very first endangered species list, which was published in 1967. Over the years, agricultural, commercial, and urban development have destroyed much of its wetland habitat, as well as much of its primary food source, the California red-legged frog. The snakes have also been a popular target for poachers and collectors.

Since 2008, SFO has been working with the USFWS on a recovery strategy for the species. Together, they’ve made enhancements to the West of Bayshore habitat, including building rainfed ponds and deepening existing wetlands. They have also added fences to protect habitat and prevent illegal collection.

But low population counts at other locations means the recovery for the San Francisco garter snake is far from over.

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Combining genetic and demographic monitoring better informs conservation of an endangered urban snake

A San Francisco Airport Site Is Crawling With Snakes—And That’s a Good Thing

Photo, posted April 16, 2011, courtesy of Brian Gratwicke via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Forests And Climate Change | Earth Wise

June 17, 2021 By EarthWise Leave a Comment

A carbon sink is anything that absorbs more carbon from the atmosphere than it releases. Examples of carbon sinks include the ocean, soil, and plants. In contrast, a carbon source is anything that releases more carbon into the atmosphere than it absorbs. Volcanic eruptions and burning fossil fuels are two examples.

Forests are among the most important carbon sinks. Trees remove carbon from the air and store it in their trunks, branches, and leaves, and transfer some of it into the soil. But in many regions, deforestation, forest degradation, and the impacts of climate change are weakening these carbon sinks. As a result, some climate activists advocate for large-scale tree-planting campaigns as a way to remove heat-trapping CO2 from the atmosphere and help mitigate climate change.

But according to a new study recently published in the journal Science, planting new trees as a substitute for the direct reduction of greenhouse gas emissions could be a pipe dream. While planting trees is easy, inexpensive, and can help slow climate warming, the ongoing warming would be simultaneously causing the loss of other trees. Instead, the research team says it makes more sense to focus on keeping existing forests healthy so they can continue to act as carbon sinks, and to reduce emissions as much as possible and as quickly as possible.

But keeping forests healthy will require a paradigm shift in forest management. Instead of trying to maintain forests as they were in the 20th century, the research team says forests need to be managed proactively for the changes that can be anticipated.

One thing is clear: We cannot plant our way out of the climate crisis.

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Forests and climate change: ‘We can’t plant our way out of the climate crisis’

Photo, posted August 9, 2015, courtesy of Nicholas A. Tonelli via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Prickly Pear As A Sustainable Crop | Earth Wise

April 6, 2021 By EarthWise Leave a Comment

The fruits and pads of opuntia, better known as prickly pear cactus, find their way into people’s diets in many arid and semi-arid places around the world. In Mexico, the pads are known as nopales and are used in a variety of dishes. The pears themselves are used in jams, salads, and juices.

A five-year study by the University of Nevada Reno College of Agriculture, Biotechnology & Natural Resources investigated the prospects for cactus pear to become a major crop like soybeans and corn and to help provide a biofuel source.

As the climate changes, dry areas are going to get dryer and drought issues will increasingly affect traditional crops.

The study looked at the particular opuntia species called the spineless cactus pear and found that it had the highest fruit production while using up to 80% less water than some traditional crops. Cactus pear can be used for both human consumption and livestock feed. As a perennial crop, once the fruit and pads are harvested for food, the remaining biomass can be used for biofuel production.

Corn and sugar cane are the most utilized bioenergy crops right now, but these use three to six times more water than cactus pear. The cactus pear productivity is on par with corn and sugar cane, but not only do they use a fraction of the water, they also have higher heat tolerance.

Over 40% of land area around the world is classified as semi-arid or arid. There is enormous potential for planting cactus for carbon sequestration. If nothing else, it makes great sense to grow cactus pear crops in abandoned areas that are marginal and may not be suitable for other crops.

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Study shows cactus pear as drought-tolerant crop for sustainable fuel and food

Photo, posted April 16, 2020, courtesy of Kevin Dooley via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Renewable Growth During The Pandemic | Earth Wise

December 22, 2020 By EarthWise Leave a Comment

According to a new report published by the International Energy Agency, global renewable energy installations will hit a record level in 2020 in sharp contrast with declines in the fossil fuel sectors caused by the Covid-19 pandemic.

For the year, almost 90% of all new electricity generation will be renewable, with only 10% powered by gas and coal. This progress puts green power on track to become the largest global electricity source by 2025, displacing coal-powered generation, which has been dominant for the past 50 years. By that year, renewables are expected to supply one-third of the world’s electricity.

Solar power capacity has increased by 18 times since 2010 and wind power by four times. In 2010, hydropower provided 77% of the world’s green power, but its share has fallen to 45% – not because there is less hydropower but because solar and wind have grown so much.

Growing recognition of the need to tackle the global climate crisis has made renewable energy increasingly attractive to investors. According to the IEA report, shares in renewable equipment makers and project developers have outperformed most major stock market indices and the value of shares in solar companies has more than doubled in the past 12 months. Fossil fuels have had a turbulent time in 2020 as the pandemic has caused demand from transport and other sectors to plunge.

While renewables continue to see dramatic growth in electrical generation capacity, electricity represents only about one-fifth of all energy use. The burning of fossil fuels in transport, industry, and heating continues to make up the bulk of energy emissions.

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Renewable energy defies Covid-19 to hit record growth in 2020

Photo, posted October 2, 2020, courtesy of the Bureau of Land Management California via Flickr. Photo credit: Clearway Energy Group.

Earth Wise is a production of WAMC Northeast Public Radio.

Shrinking Alaskan Salmon | Earth Wise

September 24, 2020 By EarthWise Leave a Comment

According to a new study published in the journal Nature Communications, salmon returning to Alaskan rivers have become significantly smaller over the past 60 years. As a result of climate change and competition from hatchery fish, wild salmon are spending less time at sea and are returning to spawning grounds at younger ages.

The study, by scientists at the University of Alaska at Fairbanks and the University of California Santa Cruz, examined measurements of over 12 million fish collected by the Alaska Department of Fish and Game from 1957 through 2018. Over that time period, four out of Alaska’s five wild salmon species – Chinook, chum, coho, and sockeye – have shrunk in size. Chinook salmon is the official state fish of Alaska and they used to stay out at sea for seven years before returning to spawn. Many are now returning to rivers at just four years old and are on average 8% smaller than they were 30 years ago.

The shrinking size of Alaskan salmon has consequences for people, the economy, and ecosystems in Alaska. Wild salmon is a staple food for many residents of the state, particularly among indigenous groups. More generally, Alaska produces nearly all of the wild salmon in the U.S. Commercial fishing of over 200 million wild salmon in 2019 resulted in $657 million in income. The fish are also an important food source for bears and other wildlife and the spawning migration of salmon plays an important role in nutrient transportation in Alaskan river ecosystems.

Multiple factors are driving the changes in the salmon population, but the largest effects are the changing climate and the abundance of salmon in the ocean due in part to hatchery production that results in competition for the salmon’s food.

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Alaska’s Salmon Are Significantly Smaller Than They Were 60 Years Ago

Photo, posted September 5, 2019, courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Renewables Surpass Coal | Earth Wise

July 3, 2020 By EarthWise Leave a Comment

In 2019, energy consumption in the U.S. from renewable sources exceeded consumption from coal for the first time since before 1885. This has come about from a combination of the continued decline in the amount of coal used for electricity generation as well as the continued growth in renewable energy, mostly from wind and solar.

Until the mid-1800s, burning wood was the main source of energy in the U.S. and, in fact, it was the only commercial-scale renewable energy source until the first hydroelectric plants came online in the 1880s. Coal was used as fuel for steamboats and trains and making steel but only started to be used to generate electricity in the 1880s.

In 2019, U.S. coal consumption decreased for the sixth consecutive year and fell to its lowest level in 42 years. Natural gas has displaced much of the energy generation from retired coal plants.

At the same time, renewable energy consumption in the U.S. grew for the fourth year in a row to a record high level, almost entirely as a result of the growing use of wind and solar power. In 2019, wind power surpassed hydroelectric power for the first time and is now the most-used source of renewable energy for electricity generation in the U.S.

Coal was once commonly used in the industrial, transportation, residential, and commercial sectors. Today, in the U.S., it is mostly used to generate electricity, and that use is rapidly declining.

Electricity consumption for 2020 is likely to be anomalous in many ways as a result of the Covid-19 pandemic shutdowns. From all indications, however, the role of renewable energy will only have been increased during the shutdown period.

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U.S. renewable energy consumption surpasses coal for the first time in over 130 years

Photo, posted July 26, 2013, courtesy of Don Graham via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

PPE Pollution | Earth Wise

June 25, 2020 By EarthWise Leave a Comment

While the COVID-19 pandemic and its shutdown of so many human activities has reduced many kinds of pollution, it has also managed to create a new source of pollution: face masks and sanitary gloves.

Divers from a French non-profit organization called Operation Clean Sea are already finding gloves, masks, and hand sanitizer bottles beneath the waves of the Mediterranean, along with the usual litter of disposable cups and aluminum cans. In France, authorities have ordered 2 billion disposable masks. Given that, there may soon be the risk of having more masks in the Mediterranean than jellyfish. In Hong Kong, face masks have been piling up on beaches and nature trails. Even in Hong Kong’s isolated and uninhabited Soko Islands, dozens of masks are showing up on a small stretch of beach.

Disposable masks may feel like soft cotton, but almost all of them are made from non-biodegradable material such as polypropylene. When such masks are discarded into storm drains, they end up in rivers and seas. With a lifespan of hundreds of years, these masks are an ecological timebomb. Land-based activity accounts for 80% of ocean pollution, and half of that is a direct result of single-use plastics. Many of the CDC’s recent recommendations for reopening offices and businesses actually recommend the increased use of them, and for sensible reasons.

The best we can all do is to wear reusable masks and to try to wash our hands more often rather than putting on another pair of latex gloves. Given that there are alternatives, we don’t need to make plastic the solution to protect us from Covid-19.

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COVID-19 Masks Are Polluting Beaches and Oceans

Photo, posted March 28, 2020, courtesy of Michael Swan via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Methane-Eating Bacteria And Greenhouse Gas Emissions | Earth Wise

May 20, 2020 By EarthWise Leave a Comment

One of the great concerns about the warming Arctic temperatures is that thawing permafrost will release alarming amounts of methane into the atmosphere. Organic material in the permafrost begins to decompose when temperatures rise, and methane is released in the process.

Methane is a far more potent greenhouse gas than carbon dioxide. Methane’s lifetime in the atmosphere is much shorter than carbon dioxide, but it is more efficient at trapping radiation. Pound for pound, the comparative impact of methane is more than 25 times greater than carbon dioxide.

A new study, published by scientists at Purdue University, has discovered a type of methane-oxidizing bacteria living in upland Arctic soils that could potentially be reducing the amount of methane emitted by decomposing permafrost.

The findings of the research indicate that the net greenhouse gas emissions from the Arctic may be much smaller than previously modeled because of the increased productivity of a type of bacteria known as high affinity methanotrophs, or HAMs. This group of bacteria uses atmospheric methane as an energy source. The emissions from wetlands will potentially be very large, but the contribution from the uplands will be mitigated by the bacteria.

Organic-rich soils, including permafrost, comprise only 13% of the Arctic land area and are the major source of methane emissions. The other 87% of the region is dominated by mineral-rich soils that support HAMs. Because of this, overall methane emissions continue to be less than climate models have predicted.

While this is good news, the researchers warn that Arctic emissions overall will continue to increase as shown in other studies.

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Methane-Eating Bacteria Could Help Decrease Greenhouse Gas Emissions From Thawing Arctic Tundra

Photo, posted July 12, 2016, courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

A Hidden Source Of Arctic Carbon | Earth Wise

April 24, 2020 By EarthWise Leave a Comment

Researchers from the University of Texas at Austin, the U.S. Fish and Wildlife Service, and Florida State University have published a paper presenting evidence of significant and previously undetected concentrations and fluxes of dissolved organic matter entering Arctic coastal waters. The source of the organic matter is groundwater flow atop the frozen permafrost. The groundwater moves from land to sea unseen, but the new research reveals that it carries significant concentrations of carbon and other nutrients to Arctic coastal food webs.

Globally, groundwater is important for delivering carbon and other nutrients to oceans, but in the Arctic, where much water is trapped in the permafrost, its role was thought to be minimal. But the new research reveals that groundwater may be contributing an amount of dissolved organic matter to the Alaskan Beaufort Sea that is comparable to what comes from neighboring rivers during the summer.

The researchers found that shallow groundwater flows beneath the surface and picks up new, young organic carbon and nitrogen, but it also mixes with layers of deeper soils and thawing permafrost, picking up and transporting century-to-millennia old organic carbon and nitrogen. This material is unique because it is directly transported to the ocean without seeing or being photodegraded by sunlight and may be valuable as a food source to bacteria and higher organisms that live in Arctic coastal waters.

The study concluded that the supply of leachable organic carbon from groundwater amounts to as much as 70% of the dissolved organic matter that enters the Beaufort Sea from rivers during the summer. The role that groundwater inputs play in Arctic coastal ecosystems will be an area of active research for years to come.

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Hidden Source of Carbon Found at the Arctic Coast

Photo, posted June 14, 2015, courtesy of Eugen Marculesco via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Wind Power Overtakes Hydroelectric Power | Earth Wise

April 10, 2020 By EarthWise Leave a Comment

In 2019, the amount of electricity generated by wind power surpassed hydroelectric power for the first time, making wind the largest renewable source of electricity generation in the country.

Total wind generation in 2019 was 300 million MWh, which was 26 million MWh more than was produced by hydroelectric plants.

Hydroelectric generation has fluctuated between 250 and 320 million MWh over the past decade. The capacity base has been stable, so the fluctuations were a result of variable annual precipitation. Hydroelectric generation is generally greatest in the spring when rain and melting snow pack increase water runoff.

The growth in wind power is primarily a result of increasing capacity rather than any major fluctuations in wind caused by changing weather. The U.S. added about 10 GW of wind capacity in 2019, making it the second largest year for capacity additions ever, second only to 2012.

Wind energy is an intermittent source, meaning that it isn’t windy all the time. The average annual capacity factor for the U.S. wind fleet over the past decade has been 28 to 35%, meaning that is the amount of energy actually produced compared with the systems running at continuous full power all the time. By comparison, the U.S. hydroelectric fleet operated at 35 to 43% of capacity during that period. So, wind power is actually not that much less a steady source than hydroelectric power.

According to the U.S. Energy Information Administration, the government’s production tax credit, which was extended through this year, means that wind power capacity in the U.S. will continue to grow at a robust pace. Meanwhile, some dams are being decommissioned and there is little new construction in the hydropower sector.

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Wind has overtaken the top position for renewable generation in the U.S., EIA says

Photo courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

The Arctic As A Carbon Source

December 16, 2019 By EarthWise Leave a Comment

According to a new NASA-funded study, the Arctic may now be a source for carbon in the atmosphere rather than being the sink for it that is has been for tens of thousands of years.

The study, published in Nature Climate Change, warns that carbon dioxide loss from the world’s permafrost regions could increase by more than 40% over the next century if human-caused greenhouse gas emissions continue at their current pace. Worse yet, carbon emitted from thawing permafrost has not even been included in most climate models.

Permafrost is the carbon-rich frozen soil and organic matter that covers nearly a quarter of Northern Hemisphere land area, mostly in Alaska, Canada, Siberia, and Greenland. Permafrost holds more carbon than has ever been released by humans from fossil fuel burning, but it has been safely locked away by ice for tens of thousands of years.

As global temperatures rise, the permafrost is starting to thaw and release greenhouse gases into the atmosphere.

The recent findings indicate that the loss of carbon dioxide during the winter in the Arctic may already be offsetting carbon uptake during the growing season. The researchers compiled on-the-ground observations of carbon dioxide emissions across many sites and combined these with remote sensing data and modeling. They estimate that the permafrost region is now losing 1.7 billion metric tons of carbon during the winter season but taking up only 1 billion during the growing season.

The major concern is that as the Arctic continues to warm, more carbon will be released into the atmosphere from the permafrost region, which will further the warming. Climate modeling teams across the globe are trying to incorporate these findings into their projections.

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Arctic Shifts to a Carbon Source due to Winter Soil Emissions

Photo, posted July 27, 2015, courtesy of Gary Bembridge via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Emissions-Free Cement

October 29, 2019 By EarthWise Leave a Comment

The production of cement – which is the world’s leading construction material – is a major source of greenhouse gas emissions, accounting for about 8% of global man-made emissions.

Cement production produces carbon dioxide in two ways: from a key chemical process and from burning fuel to produce the cement. The process of making “clinker” – the key constituent of cement – emits the largest amount of CO2. Raw materials, mainly limestone and clay – are fed into huge kilns and heated to over 2,500 degrees Fahrenheit, requiring lots of fossil fuel. This calcination process splits the material into calcium oxide and CO2. The so-called clinker is then mixed with gypsum and limestone to produce cement.

A team of researchers at MIT has come up with a new way of manufacturing cement that greatly reduces the carbon emissions. The new process makes use of an electrolyzer, where a battery is hooked up to two electrodes in water producing oxygen at one electrode and hydrogen at the other. The oxygen-evolving electrode produces acid and the hydrogen-evolving electrode produces a base. In the new process, pulverized limestone is dissolved in the acid at one electrode and calcium hydroxide precipitates out as a solid at the other.

High-purity carbon dioxide is released at the acid electrode, but it can be easily captured for further use such as the production of liquid fuels or even in carbonated beverages and dry ice. The new approach could eliminate the use of fossil fuels in the heating process, substituting electricity generated from renewable sources.

The process looks to be scalable and represents a possible approach to greatly reducing one of the perhaps lesser known but nevertheless very significant sources of greenhouse gas emissions.

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New approach suggests path to emissions-free cement

Photo, posted March 26, 2014, courtesy of Michael Coghlan via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Trees And Methane

August 14, 2019 By EarthWise Leave a Comment

The Amazon is a source of many mysteries. One that was as troubling as it was mysterious was the large amounts of methane emissions coming from the rainforest that were observed by satellites but that nobody could find on the ground. In total, there were 20 million tons of methane whose origin was unknown.

An expedition by a British postdoctoral researcher who spent two months strapping gas-measuring equipment to thousands of trees has solved the mystery. It turns out that trees, especially in the extensive flooded forests, were stimulating methane production in the waterlogged soils and pumping it into the atmosphere.

This research has uncovered a previously-ignored major source of the second most important greenhouse gas in the world. Apparently, most of the world’s estimated 3 trillion trees emit methane at least some of the time.

This in no way implies that trees are bad for the climate and therefore should be cut down. The reality is that the carbon storage capability of trees far outweighs their methane emissions. But since corporations these days are planting trees to offset their carbon emissions, it is essential to know if their numbers add up. Carbon accounting has to include the complex chemistry of trees and methane.

Wetland tree trunks can act as passive conduits for methane generated by micro-organisms in waterlogged soils. The solid-looking trunks contain spaces and channels through which gases travel up and down. But in wetland systems, trees also create the conditions, and provide the raw materials, for methane generation by micro-organisms. Trees are essentially bioreactors. Some trees even actively generate methane from photochemical reactions in their foliage.

Understanding the interactions of ecosystems and the atmosphere is a complicated business.

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