Ideas for Composting and Why Soil Carbon Matters for Climate Action


Spring is here and Lucy is planning to compost again. She has had most success with composting when it is not kept in a container, as it was easy to mix periodically. In the past, she had a great spot around the corner of the house where no-one could see it. Now, since it must go in the yard, she thinks it will need some containment. Past experience has taught her that it is not good to throw a ton of sod or grass clippings into the compost all at once, as this does not yield success. Reading up now, we are learning that a layering of compost is required to be successful, with air being one of the layers. Turn the compost every few weeks to aerate it.

Here are the two other main ingredients required for success in compost, as tips from are teaching us:

“Nitrogen or protein-rich matter-green material (manures, food scraps, green lawn clippings, kitchen waste, and green leaves) provides raw materials for making enzymes.”

“Carbon-rich matter-brown material(like branches, stems, dried leaves, peels, bits of wood, bark dust or sawdust pellets, shredded brown paper bags, corn stalks, coffee filters, coffee grounds, conifer needles, egg shells, straw, peat moss, wood ash) gives compost its light, fluffy body.” 

“A healthy compost pile should have much more carbon than nitrogen. A simple rule of thumb is to use one-third green and two-thirds brown materials. The bulkiness of the brown materials allows oxygen to penetrate and nourish the organisms that reside there. Too much nitrogen makes for a dense, smelly, slowly decomposing anaerobic mass. Good composting hygiene means covering fresh nitrogen-rich material, which can release odors if exposed to open air, with carbon-rich material, which often exudes a fresh, wonderful smell. If in doubt, add more carbon!”

The bottom layer is best  placed on the ground to allow critters like worms to get into the compost. Do not put in anything with oil or meat or bones, as that will smell and attract animals. Avoid putting in weeds too. If your compost is in the sun, it will break down faster. If you get a lot of rain, a cover will be essential as you like to have moist compost but not wet compost. You may need to water it once and awhile if it gets too dry.

One can buy compost bins of all sorts. Lucy once had a black one with a lid but could not stir it and it felt too small. She now thinks the tumbler ones that rotate are likely easier, and read somewhere that they are ideal at a 3’ by 3’ size, but can be bigger or smaller. One close to the back of the house to make dumping in the food scraps is handy. However, Lucy is putting hers farther away to avoid issues with critters, smell and any other unexpected problems.

The compost created makes for the best nutrient rich humus for your garden or lawn, and ends up costing very little.  It can divert up to 30% of household waste going into the landfill. “That’s important because when organic matter hits the landfill, it lacks the air it needs to decompose quickly. Instead, it creates harmful methane gas as it breaks down, increasing the rate of global warming and climate change.” (For more info on food waste and climate change, visit our March 5th Blog post at .)


Where you can get compost in Edmonton

If you want to pick up free compost in Edmonton, one place offering this is Green and Gold Gardens from the cow barn.

For a reasonably priced option, and one that supports community groups as a fundraiser, you can go to Clean It Green It. They have two locations, one in Strathcona and one in the west end, and you can order online for delivery too. The hours for pick up are Friday 9-6 and Saturday 9-1 for the month of May. Check out their website.

Edmonton: New Garbage Program Will Let the City Do Your Composting

Between 2020 and 2022 Edmonton will roll out the new garbage pick up system that will include separation of food waste, so if you do not want to compost, the city will do it for you. You will receive a kitchen food waste bin for under your sink. It seems slow in coming, but Lucy is very excited to be seening this program finally happen. Many other cities are already doing this. In Toronto, for example, separate compost bins have been part of weekly garbage pick up service for a number of years. Fortunately this service continues as an essential service under the COVID pandemic lockdown, and just recently spring yard waste collection was added onto the list too.

Soil Carbon & Climate Change

What is soil carbon sequestration? Is it a plus or minus for offsetting rising atmospheric carbon emissions and slowing global warming?

The short answer is, well it is a complicated matter, but holds the potential to be beneficial.  At least, this is what we are learning as we only just begin to scratch the surface on a vast and complex area of science.

According to the UN Food and Agriculture Organization (FAO), soil carbon sequestration (or storage) warrants, and recently is garnering, greater attention by scientists and policymakers for its potential as an added tool for effectively combatting global warming and climate change.

Let’s start with some basics.

What is Soil Carbon Sequestration?

We found this to be a helpful, informative answer, from the Ecological Society of America (ESA),

“Carbon is found in all living organisms and is the major building block for life on Earth. Carbon exists in many forms, predominantly as plant biomass, soil organic matter, and as the gas carbon dioxide (CO2) in the atmosphere and dissolved in seawater.  Carbon sequestration is the long-term storage of carbon in oceans, soils, vegetation (especially forests), and geologic formations. Although oceans store most of the Earth’s carbon, soils contain approximately 75% of the carbon pool on land – three times more than the amount stored in living plants and animals. Therefore, soils play a major role in maintaining a balanced global carbon cycle.’

So, just as we have been learning, sharing and putting the emphasis to-date in our our blog posts about “why trees matter,” now we are beginning to learn as well about “why soil matters”.

Why Does Soil Carbon Matter?

Like trees, soil can act as a carbon sink or carbon pool.  This is a beneficial function, as the FAO describes because – “Atmospheric concentrations of carbon dioxide can be lowered either by reducing emissions or by taking carbon dioxide out of the atmosphere and storing in  terrestrial, oceanic, or freshwater aquatic ecosystems. A sink is defined as a process or an activity that removes greenhouse gas from the atmosphere.

From here, it gets a bit more complicated, with human activity in terms of land-use practices, greatly affecting whether soil carbon is a plus or minus in terms of climate change.

It all depends on whether the carbon stays stably captured in soil (beneficial), or if it gets released into the atmosphere, making matters worse. As a article puts it succinctly, “Soil carbon storage is a vital ecosystem service, resulting from interactions of ecological processes. Human activities affecting these processes can lead to carbon loss or improved storage.”

The FAO explains that, “The long-term conversion of grassland and forestland to cropland (and grazing lands) has resulted in historic losses of soil carbon worldwide but there is a major potential for increasing soil carbon through restoration of degraded soils and widespread adoption of soil conservation practices.”

“FAO is concerned with the effect of agriculture on climate change, the impact of climate change on agriculture and with the role that agriculture can play in mitigating climate change. Historically, land-use conversion and soil cultivation have been an important source of greenhouse gases (GHGs) to the atmosphere. It is estimated that they are still responsible for about one-third of GHG emissions.” (concerning)

“However, improved agricultural practices can help mitigate climate change by reducing emissions from agriculture and other sources and by storing carbon in plant biomass and soils….The development of agriculture during the past centuries and particularly in last decades has entailed depletion of substantive soil carbon stocks. Agricultural soils are among the planet’s largest reservoirs of carbon and hold potential for expanded carbon sequestration (CS), and thus provide a prospective way of mitigating the increasing atmospheric concentration of CO2. It is estimated that soils can sequester around 20 Pg C in 25 years, more than 10 % of the anthropogenic emissions. (Better news and promising potential)

Other articles and reports help to quantify the potential of soil carbon sequestration in the efforts to combat global warming and climate change. For example, excerpts below from this Yale University article, “Soil as Carbon Storehouse: New Weapon in Climate Fight?” help us to understand the scale of either the threat (if soil carbon keeps being released) or potential benefit to help curb global warming (via changing behaviours toward greater carbon storage in soils). It also points out some promising shifts in land use practices for strengthening soil carbon capture.  Turns out there is more to soil than simply the brown stuff we put plants and trees into!

“Scientists say that more carbon resides in soil than in the atmosphere and all plant life combined; there are 2,500 billion tons of carbon in soil, compared with 800 billion tons in the atmosphere and 560 billion tons in plant and animal life. And compared to many proposed geoengineering fixes, storing carbon in soil is simple: It’s a matter of returning carbon where it belongs….”

“According to Rattan Lal, director of Ohio State University’s Carbon Management and Sequestration Center, the world’s cultivated soils have lost between 50 and 70 percent of their original carbon stock, much of which has oxidized upon exposure to air to become CO2. Now, armed with rapidly expanding knowledge about carbon sequestration in soils, researchers are studying how land restoration programs in places like the former North American prairie, the North China Plain, and even the parched interior of Australia might help put carbon back into the soil.”

“Absent carbon and critical microbes, soil becomes mere dirt, a process of deterioration that’s been rampant around the globe. Many scientists say that regenerative agricultural practices can turn back the carbon clock, reducing atmospheric CO2 while also boosting soil productivity and increasing resilience to floods and drought. Such regenerative techniques include planting fields year-round in crops or other cover, and agroforestry that combines crops, trees, and animal husbandry….”

Lal argues that soil carbon could (should) play a vital role in efforts to combat global warming, shifting the current focus on efforts to curb emissions of fossil fuels, to include a sharper focus to add soil carbon sequestration into the toolkit.

“The top priorities, he says, are restoring degraded and eroded lands, as well as avoiding deforestation and the farming of peatlands, which are a major reservoir of carbon and are easily decomposed upon drainage and cultivation. 

He adds that bringing carbon back into soils has to be done not only to offset fossil fuels, but also to feed our growing global population. ‘We cannot feed people if soil is degraded,’ he says…. According to Lal, some pools of carbon housed in soil aggregates are so stable that they can last thousands of years. This is in contrast to “active” soil carbon, which resides in topsoil and is in continual flux between microbial hosts and the atmosphere. ”

Promising Agricultural and Agroforestry Practices

“As basic as soil carbon is, there’s much scientists are just learning about it, including how to make the most of its CO2 sequestration capacity. One promising strategy, says Goreau, is bolstering soil microbiology by adding beneficial microbes to stimulate the soil cycles where they have been interrupted by use of insecticides, herbicides, or fertilizers. As for agroforestry, programs with greater species diversity are better able to maximize the storage of carbon than monocultures. Many researchers are looking to biochar — produced when plant matter, manure, or other organic material is heated in a zero- or low-oxygen environment — for its ability to turn problem areas into productive sites while building soil carbon. Says Goreau, “Vast areas of deforested land that have been abandoned after soil degradation are excellent candidates for replanting and reforestation using biochar from the weeds now growing there.” 

“Our understanding of soil microbiology and how soil life affects the carbon cycle is poised for tremendous growth, says Goreau. This, he says, is thanks to the burgeoning field of metagenomics, the study of genetic material from specimens taken directly from the environment rather than cultured in a lab. “For the first time,” says Goreau, “we can identify all major soil biogeochemical pathways from the genetic information in the microbes.” 

“Even at our current level of knowledge, many see great potential for storing carbon in soil. Lal of Ohio State says that restoring soils of degraded and desertified ecosystems has the potential to store in world soils an additional 1 billion to 3 billion tons of carbon annually, equivalent to roughly 3.5 billion to 11 billion tons of CO2 emissions. (Annual CO2 emissions from fossil fuel burning are roughly 32 billion tons.) “

Source: Yale University article

Soil Carbon and Climate Change

We are learning from scientists that, “Approximately two-thirds of the total increase in atmospheric CO2 is a result of the burning of fossil fuels, with the remainder coming from SOC loss due to land use change (Lal 2004), such as the clearing of forests and the cultivation of land for food production….”

“Despite the much larger size of the oceanic carbon pool relative to the soil carbon pool, the rate of exchange between the atmosphere and the soil is estimated to be higher than that between the atmosphere and the ocean. …Although there is interest in increasing oceanic carbon storage rates through large-scale nutrient additions, there is skepticism towards this approach due to the unknown consequences on global nutrient cycles and marine ecosystems (Cullen & Boyd 2008). The goal of increased storage of carbon in soil has received much wider acceptance due to a better understanding of the processes involved in SOC storage, more direct control of these processes through human activities, and the other known ecosystem benefits to be obtained by increasing SOC, including benefits to water quality and increased food security.”

This summary chart points the way forward for how changes in land-use practices can contribute positive benefits in reducing harmful carbon release into the atmosphere or increasing soil carbon sinks or both.

Source: The Nature Education Knowledge Project web-page on Soil Carbon Storage at:

Soil Control in Tanzania – Video

We close with this 10-minute video clip by the UN on Soil Control in Tanzania. It offers glimpses of a majestic Mount Kilimanjaro in the background, while providing further enrichment for our understanding of the complex ecological-human inter-connections and many balancing factors and needs in addressing climate action and food and water security.

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