Demand for the product made by Compost Cats, a University of Arizona student-run organization that turns food and yard waste into nutrient-rich soil, has outstripped supply.
What makes this recycled dirt so special?
Arizona, like the rest of the desert Southwest, has a much lower amount of water and nutrients in its soils than less arid parts of the country – which is where compost comes in handy.
"Compost acts as a soil amendment by adding some of those lacking nutrients and raising the water retention abilities of the soil," said Madeline Ryder, a Compost Cats member and a UA senior double majoring in natural resources and environmental studies.
"It's much better for the environment and safer to use than chemical fertilizers," Ryder said.
Composting is a process of turning organic waste such as food scraps, manure and landscape clippings into high-nutrient soil that can be reused for agriculture and gardening. Nutrients in food waste and garden clippings remain in the waste after it is broken down during the composting process, and can be reabsorbed by plants when compost is added to the soil.
And if compost is being used as a substitute for chemical fertilizers, there are even more benefits, she said, "including the reduced emissions from producing those fertilizers and adding less chemicals into the environment, which could eventually end up in our groundwater supply or washes."
In addition, "food waste that would normally go in the landfills would create methane, a greenhouse gas that is 20 or 30 times more potent than carbon dioxide, from the process used to break it down," Ryder said.
Food waste in landfills is not turned regularly to let oxygen into the waste heaps, allowing for methane-producing bacteria to take over landfill garbage dumps.
Since compost heaps are turned over regularly, oxygen is allowed to mix with the waste material and encourages oxygen-loving bacteria to colonize the compost and break down the food scraps without releasing the vast quantities of harmful methane gas that are produced in landfills.
"One of the main goals that is unique to Compost Cats is to reduce as much organic material going into landfills as possible," Ryder said. "This reduces the amount of methane produced by landfills and the need for chemical fertilizers at the same time."
While digesting and breaking down the scraps, the activity of the bacteria produces enormous amounts of heat, making compost piles as hot as 140 to 160 degrees Fahrenheit.
"In the wintertime, compost piles steam," Ryder noted.
"We make sure that it stays at that temperature for four weeks," she added. "The process ensures that there are no pathogens in the compost that could be transferred to the next crop."
The group turns its compost regularly and "we don't add anything to it except water," Ryder said.
Although the students are collecting food and yard waste not just from campus, but also from Tucson businesses, there isn't enough for the home gardeners who visit the group's website to place their orders.
That should change soon thanks to a new partnership between Compost Cats – a program under the Associated Students of the University of Arizona – and the city of Tucson, which will enable to group to extend its composting service to many more Tucson businesses. By fall, Compost Cats hopes to boost its operations and get caught up on orders.
"We are confident that this fall we will be able to supply more compost than we've ever been able to in the past," Ryder said.
Lots of people around Tucson will be happy to hear that.
"Most of the comments we receive are about how wonderful our program is from a sustainability and student leadership perspective," Ryder said. "I feel like older generations, who are our main customers, are glad to see younger generations interested in bettering the community."