Study Notes on Food Waste and Glass Production

Authors: I.A. Cornejo, S. Ramalingam, J.S. Fish, I.E. Reimanis
Focus: Novel use of food waste as a resource for producing glass and related materials.

Health and Environmental Problems: Food waste contributes to significant health risks and environmental degradation which translate into direct economic costs.
Economic Costs: The Food and Agriculture Organization reports that the global direct economic cost of food waste is $750 billion. This includes both upstream costs of production and downstream waste management costs.
**Municipal Solid Waste Statistics:
- U.S.: 250 million tons of municipal solid waste (MSW) produced annually; roughly 70 million tons (28 wt%) is organic.
- Food waste constitutes approximately 35 million tons (14.5 wt%) of U.S. MSW.
- European Union generates about 89 million tons of food waste yearly; China exceeds 40 million tons.
Pre-consumer Waste: One-third of all global fruit and vegetable production is estimated to be lost prior to reaching consumers, contributing to waste.
Organic waste value: Contains valuable resources in terms of energy, water, and minerals but is generally not utilized effectively in current disposal methods, resulting in costs associated with landfill storage and greenhouse gas emissions.

Reducing landfill mass triggers the motivation to use organic food waste as a raw material.
Potential for independence from geographical and geopolitical influences.
Although rare-earth elements are not found in plants, organic waste contains various strategic minerals.

For many years, minerals extracted from organic waste have been used for:
- Reinforcements for thermoplastics
- Production of carbides and nitrides
- Concrete manufacturing
- Fluxing agents for ceramics
- Creation of activated carbon
The usage of these minerals is limited by:
1. Limited information on mineral content in plant materials relevant to materials engineering.
2. High water and organic matter content in most food wastes, which need to be removed before mineral extraction.

Energy Costs: Energy expenses for water and organic matter removal need balancing against the recovery of valuable materials like syngas.
Varied Mineral Content: The mineral composition of food waste differs widely based on the type of plant, suggesting versatility in glass and glass-ceramic compositions.
Table 1: Lists required minerals for common glasses and their presence in food waste as measured through X-ray fluorescence (XRF).
- Some exceptions exist where minerals are not present as expected oxides, such as calcium in eggshells (present as CaCO3).
- Certain contaminants (e.g., Fe2O3) appear in low quantities, while other desirable minerals (S, Cl) may serve as fining agents.

It is challenging to detect elements like boron (important in some glasses) in food waste due to inadequate quantities or undetected forms in analysis.
Uniformity Problem: Each landfill comprises unique mineral profiles, complicating the production process.
- Suggested solutions include processing single-source streams of waste from the food industry (e.g., grains like rice, wheat, and corn) and adopting mineral extraction methodologies from the mining sector.

In 2011, global glass production reached 100 million tons, of which approximately 50% consisted of container glass (requiring 36.4 million tons of silica).
From grain alone, 20% waste (approximately 435 million tons) could yield 65 million tons of silica, sufficient to meet the glass container industry’s needs in 2011.
Significant volumes of other minerals used in glass production can also be supplied from organic food waste:
- Peanut shell: ~5 million tons waste yields 110,000 tons of CaO, 130,000 tons of K2O, and 20,000 tons of Al2O3.
- Eggshells: Approx. 50,000 tons produced annually in the U.S. provides about 50,000 tons of CaO or CaCO3 for the glass industry.

Drying: Food wastes are dried in an oven to remove moisture.
Heat Treatment: Wastes are subjected to heat to remove undesirable components (gaseous reactions produce COx, NOx).
Thermal Analysis: Monitors temperatures for removing various components (H2O, COx, etc.) during heat treatment.
In some cases, like eggshells (primary CaCO3), direct use as a raw material is possible without additional heat treatment.

The authors successfully produced four types of glasses via heating raw materials from food waste at temperatures ranging from 1,400°C to 1,550°C.
- Characterization: Optical transparency indicates amorphicity confirmed through X-ray diffraction and dilatometry.
Examples of Produced Glasses:
1. Glass 1: Soda-lime composition from rice husk and eggshell, incorporated small amounts of table salt and alumina (7.5 wt% table salt, 0.5 wt% alumina).
2. Glass 2: New calcium potassium silicate glass from rice husk, eggshells, and banana peels.
3. Glass 3: Multi-component ion-exchangeable glass from rice husk, corn husk, eggshells, and peanut shells.
4. Glass 4: Wollastonite-like glass-ceramic from rice husk, eggshells, and alumina.

Each type of glass exhibits various thermal characteristics:
- Glass transition temperatures, softening points, and coefficients of thermal expansion differ among the samples.

Investigating potential properties of new glasses from food waste in comparison to traditional mined raw materials; especially concerning trace elements and their valence states.
Ongoing efforts to catalog and analyze mineral content within organic food waste quantitatively for potential manufacturing applications.
Periodic Table Analysis: Highlights elements significant for glass manufacturing derived from organic waste, guiding future utilization of food waste.

Food waste represents a valuable, sustainable option for raw materials necessary for glass production, addressing health and environmental issues associated with organic matter in landfills.
There appears sufficient food waste available to fulfill the raw material needs for various glass products, fostering adoption in industry for both efficiency and economic viability.

Funding acknowledgment for authors from the National Science Foundation Ceramics program under grant DMR-1360565.

Extensive references provided for further reading and validation of data discussed, including cited reports, journal articles, and prior studies on food waste management and utilization in materials science.