Grantee Research Project Results
Final Report: Developmental Investigation of Recycled Color Mixed Glass in Engineered Soils
EPA Contract Number: 68HERC21C0029Title: Developmental Investigation of Recycled Color Mixed Glass in Engineered Soils
Investigators: Roark, Richard
Small Business: OLIN
EPA Contact: Richards, April
Phase: I
Project Period: March 1, 2021 through August 31, 2021
Project Amount: $99,940
RFA: Small Business Innovation Research (SBIR) - Phase I (2021) RFA Text | Recipients Lists
Research Category: Small Business Innovation Research (SBIR)
Description:
This project will develop an engineered soil product, and an engineered process, that repurposes city-wide waste-stream glass and food waste into a soil product suitable for horticultural and green infrastructure projects. The project supports the EPA’s goal to improve sustainable materials management to conserve materials and resources.
Recycling of solid waste materials, like glass, remains challenging to urban systems due to costs of recycling in comparison to landfill disposal. Process costs for glass cullet have increased, while products made from cullet have marginal commercial value. This makes glass recycling economically non-viable for most cities. Similarly challenging is food waste upcycling as soil compost: insufficient process or logistics infrastructure exists to take advantage of this readily developed resource at scale. A practical solution for converting local solid waste to local usable infrastructure effectively is therefore critical to improving use of these predominantly landfilled materials.
OLIN is partnering with Andela Products, Pennsylvania Recycling Markets Center and the City of Philadelphia to significantly reduce the landfilling of glass waste and food waste. The project will develop an engineered approach to converting glass waste and food compost into a refined soil product that can serve the needs of the city in urban development of green spaces and landscaping. The technology consists of an engineered soil, and an engineered process plan, that cities can implement to utilize pulverized glass, soil, and food compost amendment, to produce a clean, functional, soil product with demonstrated plant growth, and water draining potential similar to filtrating rain-garden soil blends. By reducing or potentially eliminating sand quantities with pulverized glass, the project addresses shortages of construction-grade sand, and the costs of sand use in soil preparations. This efficiency is further improved by facilitating on-site processing, and soil blending, improving the value for mixed-color, small-particle glass cullet.
Our previous and current studies have focused on horticultural and engineering performance of manufactured glass-based soil (GBS) and on costs and benefits to replacing natural sand with manufactured glass-sand in soil blends based on existing markets. In this EPA SBIR Phase 1 project we have addressed the design of a GBS prototype material and a scalable manufacturing (glass pulverizing, amendment and soil blending) process that will allow municipalities to divert waste glass into locally manufactured GBS.
The project builds on four years of previous research by taking the most effective soil blends, testing them as planting media in a pilot growth trial, and designing a manufacturing process that will produce them at minimal economic and environmental cost. The project demonstrates the potential for cities to repurpose their own waste glass and food waste into a commercially viable soil product. Our primary goals and the tasks performed to meet them are:
- Goal: Create a prototype glass-based soil (GBS) product using representative glass waste and food waste feedstock and commercially available glass processing equipment.
- Task 1: Use Andela equipment and municipal mixed-color glass cullet to produce the glass-sand used in the greenhouse planting trials.
- Goal: Refine the optimal mix ratios of glass-sand, food waste compost and mined components, in glass-based topsoil blends.
- Task 2: Perform greenhouse planting trial comparing various mix ratios.
- Goal: Facilitate production of horticulturally appropriate glass-sand (by material recovery facilities) and of glass-based topsoil (by soil blenders).
- Task 3: Develop a set of material specifications that can be shared with manufacturers and municipal partners.
- Goal: Facilitate local adoption of glass-based topsoil in green stormwater infrastructure.
- Task 4: Provide a technical planning package to Philadelphia city agencies.
We designed and produced three prototypical GBS mixes, using equipment produced and operated by our research team members at Andela Products (Task 1). These mixes were used in a 12-week greenhouse planting study and consisted of sand (either glass-sand or mined sand), natural loam, and food waste compost (Task 2). The component ratios tested are listed below, with Mix A as a control mix that approximates a conventional GSI topsoil.
The component ratios tested.
The planting trial assessed the performance of two plant species commonly used in GSI applications - Iris versicolor (IV) and Calamagrostis 'Karl Foerster' (CA) – planted in four soil mixes. A total of 128 plants were grown, under two different watering regimes, to determine overall performance and impacts of drought conditions on plant survival (8 replicates of each species in each of 4 mixes, 2 watering regimes).
In parallel to the greenhouse growth trial, OLIN and the Pennsylvania Recycling Markets Center worked with Philadelphia Parks and Recreation and a network of private and non-profit entities locally, to produce a technical plan and manufacturer specification that will facilitate the production and commercialization of glass-based soil in the region.
Summary/Accomplishments (Outputs/Outcomes):
Across watering treatments, glass-based soils compared favorably with sand-based soils.
Iris versicolor
Across all three measures of plant health (chlorophyll content, leaf browning, & final biomass), there were no significant differences between Iris versicolor specimens grown in soil containing glass vs soil containing no glass.
Calamagrostis ‘Karl Foerster’
In most cases, there was no significant difference between Calamagrostis ‘Karl Foerster’ specimens grown in soil containing glass vs soil containing no glass.
In some cases, Calamagrostis ‘Karl Forester’ was observed to perform significantly better in terms of chlorophyll content and shoot biomass when grown in soil containing glass vs soil containing no glass. Soil mix D (100% glass at a 42:28:30 ratio) may support improved shoot growth under low water conditions in comparison to sand-based soil, and merits further study.
However, leaf browning data is suggestive of the need for further study of the health of Calamagrostis ‘Karl Foerster’ when grown in soil mix C (100% glass at a 60:20:20 ratio) under low water conditions, as this species may perform less well in mix C than in sand-based soil under these conditions.
Technical Planning
The technical planning study indicates that the current volume of waste glass produced by Philadelphia residents and businesses annually (about 95,000 tons) could be sufficient to replace all mined sand used in public works green stormwater infrastructure (GSI) topsoils, city-wide (approximately 72,000 tons.) The study also shows that glass-sand, if processed in retrofitted municipal Material Recovery Facilities (MRFs), would represent a cost savings when compared to conventional mined sand. Currently, none of the glass waste that is picked up curbside by the Philadelphia Streets Dept is recycled. All of it is trucked to a private MRF, where glass is separated out of single stream recyclables and is sent to landfill along with all non-recyclable residue. This process costs the City over $140 per ton of glass, and represents a massive waste of recyclable material. Our plan includes all equipment specifications, process description and costs that would allow the current MRF to retrofit their existing facility, to capture that wasted resource and produce marketable glass-sand, cost effectively.
We have worked with a local soil blender that currently provides GSI soils to Philadelphia municipal agencies, to identify and address barriers to commercialization of glass-based soils, from the standpoint of soil manufacturers. We have also pulled together a network of local small businesses that can provide glass-sand and food waste compost for a pilot project in Phase II. These small businesses stand to benefit from new markets produced by a successful Phase II demonstration project.
Conclusions:
Phase I outcomes have supported the hypothesis that glass-based soil can provide economic and environmental benefits to municipalities, while supporting the health of the urban forest. Findings, however, also indicate that further study is needed to demonstrate long-term horticultural performance of GBS, to support a wider variety of plant species including trees. Laboratory and greenhouse findings show that, while glass-based soil can support plant growth as well as conventional manufactured soil under controlled conditions, there are differences between the two soil types, including pH and water retention. The long-term impacts of these differences need to be better understood before we can recommend widespread adoption.
This Phase I project has described the equipment and operational needs that would allow Philadelphia MRFs to separate, clean and crush glass into a glass-sand that meets our GBS soil specification. Based on Phase I cost analysis, MRFs could save money today by retrofitting their facilites in this way. The primary barriers preventing them from doing so are a predictable and clear outlet for the material (which our product will provide) and pressure from the municipality and the public to improve beneficial recycling rates. Through our collaboration with city agencies, we aim to provide the city with tools and information to assert this pressure.
From OLIN’s perspective, as a design and planning practice, the proposed end product of this project is not the glass-based soil itself, but the planning and consultation services that we provide to public and private clients that allow them to implement a glass diversion and soil processing system in their specific locations. Competition, in this context, is other design and planning firms or public entities that can provide similar services. To our knowledge, there are no competing firms or institutions that offer the expertise network and end-use specifications that meet local application needs, as well as technical manufacturing and commercialization plans in this sector. Therefore, the service that we are developing through this research is unique in our field, and gives our firm a competitive advantage in localities that desire improved glass waste and food waste management systems.
The SBIR Phase II pilot project will provide proof of concept for glass-based soil commercialization in Philadelphia. In so doing, it will support the growth, not only of the small business grantee (OLIN) but also, two other local small businesses: Bennett Compost and ReMark Glass, a local specialized glass material recycler. A successful pilot / demonstration installation will allow public and private entities to pick up our amended topsoil specification, creating a demand for the new material and by extension, new demand for the glass-sand produced by ReMark and the food waste compost produced by Bennett. It will also decrease the (economic and environmental) costs of topsoil to the City of Philadelphia and improve the city’s glass recycling rates. The proof of concept will make it possible to build new networks of public and private entities in cities across the U.S. to implement similar plans.
SBIR Phase II:
Developmental Investigation of Recycled Color Mixed Glass in Engineered Soils | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.