New findings fill knowledge gaps as states approach new national waste-reduction strategy
Experiments reveal the impacts of different organic waste products on soil chemistry and grass growth.
Image Credit: Jennifer Morash, UMD
With the White House announcing ambitious new national goals in June for boosting the recycling of organic waste to help fight climate change and promote a circular economy, research from the University of Maryland could help states and local governments get on board.
Recycling organic material like compost and yard trimmings often means putting it back into the ground to improve soil properties and increase the carbon content of disturbed soils. But not all organic waste is created equal and their effects on soil as well as the surrounding environment can differ vastly.
The new study, published in the journal Science of the Total Environment, reveals how three different types of organic waste products impact soil fertility and suitability for plant growth, and makes recommendations for how these recycled organics should be used.
“In order to have an effective strategy to manage organic waste, and put organic materials back into natural systems, you have to think about how to market and use the products that are made from recycled organic goods without creating unintended consequences,” said the study’s lead author Jennifer Morash, a postdoctoral associate in UMD’s Department of Environmental Science and Technology.
Morash’s first step was to identify the most commonly used recycled organics. She and her team interviewed topsoil dealers across the state to find out what products they sell to the state highway administration, one of the largest landowners in Maryland that has long encouraged the use of recycled organic materials in soils they manage, including miles of turf that line roads and highways. The most common material used was composted yard waste, which could include food waste, followed by mulched wood waste. In addition, the team studied biosolids from wastewater treatment facilities because biosolids-based products are commonly used in landscaping soils.
The team then experimented on samples of disturbed soil, increasing the organic matter by 2% using each of the recycled materials in a different sample to see how they changed the soil chemistry and the ability for grass to become established.
Morash and her team found that composted yard waste improved the soil’s ability to grow grass and kept the soil nutrient content at a healthy level while minimizing unnecessary release to the surrounding environment. Meanwhile, mulched wood waste made it harder for plants to access the nutrients in the soil, suggesting it should be used in conjunction with a fertilizer. On the other hand, biosolids from wastewater treatment facilities led to an excess of nutrients that could seep into groundwater or wash into local waterways, so Morash recommends they only be used at lower quantities as fertilizers applied to the ground rather than mixed in as soil amendments to increase organic matter.
These recommendations will help inform states responding to the new national strategy announced by the White House, the U.S. Department of Agriculture, the U.S. Environmental Protection Agency and the U.S. Food and Drug Administration in June, 2024, which calls on government agencies, retailers and consumers to reduce food loss and waste and increase recycling of organic materials. The recycling is intended to cut greenhouse gas emissions by keeping organic material out of landfills where it rots and emits methane and carbon dioxide. But as a relatively new practice at the national scale, most stakeholders will have to develop organic recycling strategies from the ground up.
The state of Maryland is ahead of the game, having passed legislation incentivizing organic recycling ten years ago.
“As other states begin to set policies to meet the national strategies, they’re going to be looking to Maryland to see what we’ve been doing,” Morash said. “And now, with this study, we can send out recommendations for what works, and how these materials can be used correctly.”
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The research was supported by Maryland Department of Transportation State Highway Administration (Award No: SHA/UM/5-21) and the National Science Foundation National Research Traineeship Program (Award No: 1828910). This story does not necessarily represent the views of these organizations.
The research paper, “Using organic amendments in disturbed soil to enhance soil organic matter, nutrient content and turfgrass establishment,” was published in the journal Science of the Total Environment. Co-authors of the paper include John Lea-Cox from the Department of Plant Sciences and Landscape Architecture, Extension agent Andrew Ristvey, and Sai Thejaswini Pamuru and Allen Davis from the Department of Civil and Environmental Engineering.
