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The Humble Earthworm: Waste Warrior


When someone mentions Charles Darwin, we think they’re going to talk about his landmark treatise of 1859, On the Origin of Species, or maybe his follow-up book about human evolution, The Descent of Man, but we rarely hear about his last book, The Formation of Vegetable Mould through the Actions of Worms. Catchy title aside, this book was a runaway best-seller in its day that outsold all of his other books.  The study of earthworms occupied Darwin on and off throughout his professional life. He was, after all, a geologist as well as a naturalist, and that broad view of the world allowed him to see the interplay between living organisms and the abiotic components of the ecosystems that sustain them.

The lowly earthworm performs a vital service in the carbon cycle – moving decaying plant material down into the soil and leaving their castings on top of the soil, thereby aerating and enriching it to nurture further plant growth. Jeremy Megraw in his review of Worms writes, “It is estimated that for a single acre of cultivated land, earthworms move 8 tons of earth in a year, enough to produce a new layer of earth 2 inches thick, rich in nitrogen, phosphorous and calcium.” But in today’s modern world, we have broken that cycle and instead of returning our vegetable scraps to the earth, we are sending them to the landfill where they rot, producing the powerful greenhouse gas, methane.

The main human-related greenhouse gases (GHG) are carbon dioxide, methane, nitrous oxide, and an array of fluorinated gases. The largest component of GHG emissions by far is carbon dioxide (CO2) at 80%, but methane comes in second at 11%. This seems like a distant second until you consider that methane is 28 times more effective at trapping heat in the atmosphere than CO2 and accounts for 30% of the increase in global temperatures since the Industrial Revolution. On the bright side, methane is short-lived compared to CO2 and, therefore, presents an opportunity to mitigate climate change more quickly. The United States has joined about 150 other countries in the Global Methane Pledge to reduce human-related methane emissions from their 2020 levels by 30% by the year 2030 to help stave off catastrophic global warming.

According to the United States Department of Agriculture (USDA), “Food is the single largest category of material sent to municipal solid waste landfills. In 2018, 35 million tons of food scraps went into landfills." Food is lost or wasted at several points in the journey from production to our tables due to various problems like bad weather, over-production, processing problems, and unstable markets. In 2015 the USDA and the Environmental Protection Agency (EPA) joined forces to launch the first-ever food loss and waste reduction goal, calling for a reduction of 50% by 2030. Leaders from across the food chain have stepped up to become Food Loss and Waste 2030 Champions.

We can do our part to combat that waste in our own households, too. The EPA has created a scale of residential and agricultural practices from Most Preferred to Least Preferred to help us see the big picture of food waste:


And they also provide a list of 8 steps we can take to prevent food waste at home:

1.    Plan ahead: Before you shop, make a list so you don’t buy more than you need.

2.    Serve smart: Portion control is good for your waistline, and good for reducing plate waste.

3.    Love your leftovers: put leftovers in the fridge and use within 3-4 days or freeze for later.

4.    Compost, don’t trash: Set up a home compost bin or drop your food waste at a compost center.

5.    Understand date labels: Except for infant formula, food that is properly stored should be safe until spoilage is evident.

6.    Buy and consume: Eat your perishables first!

7.    Freeze to save food: Uneaten produce can be frozen and used later in stews and smoothies.

8.    Order out wisely: Order only what you can finish and ask for a doggie bag for any leftovers.

Step 4 – composting – is the step that closes the loop on our food system, so here are some resources to help accomplish that task.

·         If you have a yard, you can use these directions from the EPA to set up your composting site.

·         If you don’t have a yard, you can set up a vermiculture system, a.k.a. a worm bin. Bins can be purchased or made and need to provide bedding, moisture, and ventilation for the worms – usually red wigglers (Eisenia foetida) – that will live there and eat up your table scraps, turning it into compost. Colorado State University Extension has created a good fact sheet to get you started: Vermicomposting: Putting Worms to Work.

·         If you’re squeamish about taking in new housemates and would rather not live with earthworms, Lomi is a company that makes a countertop composter that converts food scraps into compost overnight. Just load it up throughout the day and turn it on when you go to bed. By the end of the next day, you can harvest your compost and then fill it up again.

All of these systems are designed to produce compost, black gold for gardeners. Sprinkle compost in your houseplants, garden beds and even directly on your lawn where it will feed the microbiome of the soil, including earthworms. As the saying goes, one man’s trash is another man’s treasure – or earthworm’s treasure in this case. Aristotle was the first to understand the integral part earthworms play in the health of the land back in 350 BC. He and Darwin both would have been surprised to learn just how huge an impact they have on our food systems. While Darwin estimated that an acre of fertile land contained about 53,000 worms, modern estimates using X-ray computed tomography put that number closer to 1.75 million. The National Science Foundation reported that “some estimates have indicated that earthworms can increase overall plant productivity by about 25%” . By working with natural cycles – instead of ignoring them – we can improve crop productivity and air quality. As Darwin noted, the earthworm is “the unsung creature which, in its untold millions, transformed the land as the coral polyps did the sea”. This month we will be Food Loss & Waste 2030 Champions and close the loop on the carbon cycle by feeding the worms!

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