The Scoop on Composting: A Comprehensive Literature Review on Composting with a Focus on Grand Valley State University

Abstract

• This comprehensive literature review examines main microbial processes in composting: anaerobic, aerobic, and intermediate/cold composting, defining and assessing each.
• It covers common composting methods (large- and small-scale) that harness these microbial processes, with attention to their distinct advantages and drawbacks.
• Key efficiency strategies discussed: monitor and manage oxygen levels, moisture, temperature, and overall pile size.
• Reported benefits of composting: divert waste from landfills, improve soil nutrition/quality long-term, and increase plant growth and yield.
• Reported drawbacks: potential contamination with hazardous heavy metals, high soil salinity, nutrient regeneration can take years in poor soils, and in some cases methane production comparable to landfills (especially in anaerobic systems).
• The discussion then turns to on-campus composting at Grand Valley State University (GVSU) and at the Sustainable Agriculture Project (SAP), including past/present strategies and suggested improvements drawn from other universities.
• Proposed improvements include: on-campus options to buy back finished compost or establish a small-scale educational system; at SAP, either improve the current pile or install a smaller underground closed composting bin.

Introduction

• According to the United States Environmental Protection Agency (USEPA), in 2018 the U.S. generated approximately $63.1\ \,\text{million tons}$ of food waste, with about $56\%$ ending up in landfills where it rots and releases methane gas (harmful greenhouse gas).
• Food waste accounts for roughly $21.6\%$ of landfill content, persisting as landfilled material decomposes slowly.
• Composting is presented as a strategy to reduce landfill input, return nutrients to soil, and potentially generate profit.

The Basics of Composting

• Composting is defined as an organic waste diversion process that decomposes waste into nutrient-rich soil. Components can include: food waste, plant waste (e.g., grass clippings), animal waste, and wood-based materials (e.g., woodchips, twigs, paper, cardboard).
• Ideal carbon to nitrogen ratio (C:N) for efficient composting is commonly cited as $\text{C:N} \approx 25:1 \text{ to } 30:1.$
• The C:N ratio can be adjusted by mixing green waste (high nitrogen; e.g., food waste, grass clippings) with brown waste (high carbon; e.g., woodchips, dried leaves).
• A one-to-one biomass ratio of green to brown materials is sometimes described as forming the target $\text{C:N}$ ratio, though the exact ratio depends on material mix.
• Depending on feedstock composition, management technique, and input quantities, finished compost can form in as little as about two weeks or take years.
• Two primary decomposition pathways:
  • Aerobic composting: requires oxygen; microbes that thrive with oxygen generate heat, potentially reaching up to $T \approx 150!!\circ!!F\, (\approx 65.6!!\circ!!C)$ and even up to $160!\circ!F$ with good aeration. This rapid heating sterilizes the pile and reduces weed seeds and pathogens.
  • Anaerobic composting: lacks oxygen; often covered with tarp/lid; produces heat but not as hot as hot aerobic systems; leads to acidic conditions and slower decomposition; can emit strong odors from hydrogen sulfide and ammonia.
• Intermediate/cold composting sits between the extremes of hot (aerobic) and anaerobic processes, often turning less frequently and producing slower decomposition but less labor.
• Practical takeaway: the chosen method balances time, labor, odor control, and desired end-product quality.

Composting Methods

• Windrows (long rows): common for large-scale/industrial composting; dimensions typically $\text{width} \approx 3\text{ ft}, \text{ height} \approx 3!\text{–}5\text{ ft}, \text{ length} \approx 3!\text{–}300\text{ ft}$. Mostly aerobic and fast because surface material is exposed to oxygen.
  • Piles can be turned daily or every other day to ensure oxygen penetration; sometimes windrows are kept static (static windrow).
  • Oxygen flow can be enhanced by internal channels (pipes) or by mixing materials to improve aeration.
  • Benefits: rapid decomposition; potential to adjust temperature through aeration; difficulty: requires large quantities of input material and significant manual labor.
• Triple-bin composting: three separate piles/bins for a continuous, manageable process. 1) Bin 1: fresh organic materials, continuously added; mixed every few days. 2) When the pile reaches target conditions, transfer to Bin 2 and increase oxygen exposure; add fresh materials to Bin 1. 3) In Bin 2, decomposition continues at high temperature; once materials are particle-free and hot-to-warm, move to Bin 3 for cooling. 4) Bin 3: final cooling and completion; finished compost used on campus or elsewhere.
  • Example target temperature: around $150!\circ!F$ during active decomposition.
  • Claimed benefit: finished compost in about one month with proper attention (though actual times vary).
• Tumbler composting: round, closed bins that are manually rolled to turn the compost, promoting aeration.
  • Pros: reduces odors and deters pests; closed system minimizes rodent access.
  • Cons: anaerobic conditions can briefly occur inside when the bin is sealed; typical decomposition time is 6 months to 1 year depending on rotation frequency and input material; often more expensive equipment.
• Covered/buried-bin systems:
  • Covered bins: anaerobic; slower decomposition; reduced odors; sometimes buried in the ground with holes to allow moisture and moisture drainage; liquids can leach into surrounding soil, providing nutrients.
  • Buried buckets/holes in ground: anaerobic decomposition with holes at the bottom to allow leachate to seep into soil; the worm and microbial movement can assist surface soil nutrients; reduces visible waste from surface.
  • Ground burial method pros: minimal labor; easy to maintain; beneficial for garden beds through nutrient leachates.
  • Ground burial method cons: slow decomposition; potential animal access if not properly secured.
• Above-ground pile systems (simple piles): can be continuously fed but require turning to aerate; risk of odors if not managed; avoid meat products to minimize pests.
• Vermicomposting (worm-based composting):
  • Uses worms within a bin with bedding (e.g., newspaper, soil) and food scraps; avoid meat, dairy, and fatty foods to prevent worm aversion and microbial imbalances.
  • Advantages: reduces odor when indoors; can be done indoors with minimal space; worms add mucus and microbial diversity, potentially increasing nutrient content.
  • Considerations: worms require stable temperatures; bins should be elevated for airflow; can also be placed indoors under cool, stable conditions with a tray to catch liquid.

Compost Efficiency

• Oxygen management:
  • More oxygen supports aerobic microbes and faster decomposition.
  • Over-turning (e.g., multiple times per day) can impede heat buildup and reduce sterilization effectiveness for weed seeds and pathogens.
  • Under-turning can suppress aerobic activity and allow anaerobic conditions to take over, hindering decomposition. Temperature control and monitoring are essential.
• Moisture management:
  • Aerobic compost should be moist enough to hold shape but not so wet that it drips when squeezed.
  • If too wet: add dry materials (woodchips, paper, dried leaves) to restore porosity and aeration.
  • Anaerobic systems also require some moisture; excessively dry piles stall microbial activity.
• Material size and surface area:
  • Cutting materials into smaller pieces increases surface area, aiding both aerobic and anaerobic microbes and speeding decomposition.
  • Smaller piles also decompose faster due to greater surface exposure to microbes and, in aerobic piles, more contact with ambient oxygen.
  • However, very small piles may not reach sufficient heat in cooler environments, impacting sterilization.
• Temperature considerations:
  • Monitoring pile temperature helps ensure turnover occurs at optimal times to maximize decomposition and pathogen/weed seed sterilization.
• Summary: effective composting requires balancing oxygen, moisture, particle size, and temperature; each factor interacts with the others to determine turnover rate and end-product quality.

Benefits and Drawbacks of Composting

• Benefits:
  • Diverts waste from landfills, reducing methane emissions associated with anaerobic decomposition in landfills.
  • Improves soil quality and structure: increases water-holding capacity, enabling more efficient hydration of crops and soil microorganisms.
  • Enhances soil biodiversity, including fungi networks and earthworms, which stabilize soil and resist erosion.
  • Improves soil aeration, enabling better gas exchange for plant roots.
  • Reduces or eliminates the need for artificial fertilizers due to nutrient-rich compost.
  • Can increase plant growth and yield due to improved soil fertility.
• Drawbacks:
  • Potential presence of hazardous heavy metals in composted materials; heavy metals are not fully broken down, risking transfer to crops or alteration of soil microbiome.
  • Possible high salt content in some compost inputs, which can impair soil structure and nutrient balance.
  • In some cases, it takes years for compost to restore nutrients in degraded soils, unlike quick-acting chemical fertilizers.
  • Anaerobic systems can produce methane, a potent greenhouse gas, comparable to emissions from landfills; management is required to minimize this.
• Mitigation strategies:
  • Careful feedstock selection to avoid metals and excessive salts.
  • Prefer aerobic systems or ensure efficient aeration in anaerobic contexts to reduce methane production.
  • Gradual adoption and phased nutrient restoration to soils, especially in leached or degraded soils.

Grand Valley State University: Composting on Campus

• History and scale:
  • Campus composting program started in 2009 with a limited number of bins in two dining locations.
  • Over time, compost cans expanded to many campus buildings, housing, library spaces, athletic events, and more.
• Performance metrics and leadership:
  • By 2014, the campus diverted about 50% of waste away from landfills (as reported by the Office of Sustainability Practices).
  • By 2020, total diverted waste was approaching 70%, reflecting growth in composting activities and waste sorting education.
  • In the 2020 fiscal year, approximately $917\ \text{tons}$ of waste was collected and sent for composting, helped by the use of compostable cups, utensils, bags, and related items in dining services.
• Education and engagement:
  • Signs on waste bins clarify what can be composted vs. recycled vs. trash.
  • The Green Team (a student organization) supports education at waste stations, helping reduce contamination and promote correct sorting, especially at the start of semesters and during special events like zero-waste football games.
• The Cocoa composting facility:
  • Collected compostable materials from GVSU are processed by Cocoa, which creates windrows and uses a compost turner to produce finished compost.
  • Finished product is screened to improve texture for planting media and aeration.
  • Note: Cocoa does not return finished compost to GVSU for campus use; instead, it processes campus output and diverts it from landfills, contributing to broader environmental goals.
• Grand Valley’s on-campus SAP (Sustainable Agriculture Project):
  • SAP began in 2008, initiated by students to promote ecologically sustainable agriculture practices.
  • The SAP site has transformed degraded soil into a healthier ecosystem capable of producing crops using sustainable farming methods.
  • Current practice at SAP is predominantly anaerobic composting, with occasional turning (about once per year) to maintain pile structure and decomposition.
  • Feedstocks include produce waste from SAP’s own crops and weeds/dead crops; low brown waste results in a comparatively low C:N ratio and slower decomposition.
  • To supplement compost production, SAP sources finished compost from external suppliers (Top Grade) for use on crops when internal production is insufficient.
  • Vermicomposting at SAP has shown some effectiveness but remains limited in scale relative to farm needs.
• Challenges at GVSU campuses:
  • Permanence and scale constraints at SAP hinder long-term, stable compost infrastructure.
  • On-campus systems often face space and labor constraints, limiting the adoption of larger, more efficient systems.
• Cross-campus learning:
  • Other universities’ practices provide models for improvement, notably zero-waste dining programs and cyclical composting partnerships with external facilities.

Composting at the Sustainable Agriculture Project (SAP)

• Current setup and performance:
  • SAP manages a pile that is largely anaerobic with limited processing and slow turnover; minimal finished compost is produced for beds.
  • Occasional vermicomposting has been effective at small scales but cannot meet farm-wide requirements.
• Feedstock and processes:
  • Pile comprises mostly food waste from SAP crops and plant residues; limited brown (carbon-rich) materials lead to slower decomposition.
  • In-place composting (on beds) allows nutrients to be returned to soil but yields limited finished compost.
• Outsourcing and partnerships:
  • To meet crop needs, SAP purchases compost from external suppliers (e.g., Top Grade).
  • There is potential to expand internal composting and close the loop with in-ground, anaerobic buckets, or vermicomposting improvements.
• Perceived obstacles:
  • Permanence: the farm’s young status and changing management make it difficult to keep a stable composting structure in place.
  • Size and labor: large-scale features require substantial labor and resources; small-scale methods alone cannot keep pace with the farm’s biomass.

Composting at Other Universities

• Central Michigan University (CMU):
  • CMU has received national recognition (e.g., 2019 WasteWise College/University Partner of the Year) for sustainability and waste diversion.
  • Their dining operations implement a zero-waste program that diverts all wastes via recycling, composting, or reuse; they also partner with off-campus facilities to cycle back finished compost as soil or for campus uses (cyclical composting).
• Michigan State University (MSU):
  • MSU emphasizes source reduction, including the “Clean Plates at State” program that encourages smaller initial portions to reduce waste; if necessary, students can return for more, reducing overall waste per meal.
  • MSU donates edible food that cannot be sold to local food banks, further reducing waste.
  • On-campus composting includes anaerobic digesters and vermicomposting, with surplus compost sent to farms and some compost delivered to campus gardens; excess material is often redirected to other farms.
• Takeaway from other universities: successful models combine sorting/culture shifts with closed-loop composting, campus education, and partnerships with external composting facilities to maximize diversion and end-use of compost.

Proposed Improvements for Composting at Grand Valley and SAP

• On-campus (GVSU): close the loop and showcase the end product to students and staff.
  • Implement a small-scale system such as an anaerobic digester or a three-bin system on campus, managed by student volunteers or through educational coursework.
  • Seek grants (e.g., EPA Environmental Education Grant) to fund pilot projects and build momentum for expansion.
  • If possible, partner with Cocoa or another local facility to buy back finished compost (or hope to receive a portion of finished compost) to demonstrate the cycle from waste to reuse on campus.
  • Move toward zero-waste dining by prioritizing compostable/recyclable/reusable materials and phasing out or reducing trash can options to force diversion into compost/recycling channels.
  • Use Green Team education to raise awareness and improve waste-sorting accuracy, especially during peak times like the start of semesters and during large events (e.g., football games).
  • Consider a staged transition from campus-only to larger-scale windrows if pilot systems prove sustainable and scalable.
• SAP Improvements:
  • Improve current compost pile to be more efficient or introduce in-ground anaerobic buckets around beds to improve soil quality continuously and distribute nutrients across garden areas.
  • Increase turning frequency to introduce more oxygen and improve decomposition rates; monitor moisture and carbon-to-nitrogen ratio more rigorously.
  • Use the farm’s existing soil thermometer to guide turning schedules and determine when the pile is finished decomposing.
  • Turn to a more cyclical approach by developing a permanent but movable composting setup that can be relocated as needed while maintaining production.
  • Expand vermicomposting as a scalable, low-labor method to increase nutrient-enriched end products; integrate home/home-garden contributions via community buckets to supplement material flow.

Prototypes (Conceptual Models)

• In-ground anaerobic bucket prototype (illustrative, non-operational):
  • Design concept uses a buried bucket with holes at the bottom to allow leachate to seep into surrounding soil.
  • Worms and other invertebrates can move through the bin and soil, enhancing decomposition and nutrient distribution.
  • Low maintenance: occasional removal of material when the bucket is full; lid kept on to maintain anaerobic conditions; level with ground to avoid tripping hazards.
  • A sign near the bucket could help educate visitors about the system.
• On-campus triple-bin prototype (illustrative, not a full-scale build):
  • Wooden structure with two dividers creating three separate bins to form a continuous process: fresh materials in Bin 1, decomposed material moved to Bin 2, finished compost in Bin 3.
  • Turning occurs in Bin 1 every few days; when Bin 1 reaches desired temperature (e.g., $T \approx 150^{\circ}F\,$), move to Bin 2; Bin 2 remains hot and continues decomposition; when Bin 2 is finished, move to Bin 3 for cooling.
  • Fresh materials can continue to be added to Bin 1 to maintain a steady cycle.
  • Goal: provide a classroom/educational model illustrating practical workflow for student engagement.

Connections to Foundational Principles and Real-World Relevance

• Environmental sustainability:
  • Composting diverts organic waste from landfills, reducing methane emissions and contributing to climate-change mitigation strategies.
• Soil health and agronomy:
  • Compost improves soil structure, water retention, nutrient content, and microbial biodiversity; enhanced aeration supports plant root growth and resilience.
• Waste management education:
  • Campus-based programs (signage, student Green Team, zero-waste events) promote behavior change and community engagement with sustainability.
• System thinking and circular economy:
  • Proposals aim to close the compost loop by producing, returning, and reusing finished compost within the university and local farms.

Ethical, Philosophical, and Practical Implications

• Ethical: proper handling of waste to minimize environmental harm and protect public health; avoiding heavy metals and contaminants in compost feeds into ethical stewardship of campus resources and local ecosystems.
• Philosophical: emphasizes a shift from waste disposal to resource recovery, reflecting sustainable philosophies and intergenerational equity.
• Practical: requires organizational buy-in, funding, volunteer engagement, and coordination with external facilities; success depends on consistent operations, education, and monitoring.

Key Numerical References, Formulas, and Definitions (LaTeX)

• Carbon to nitrogen ratio: $\text{C:N} \approx 25:1\ \text{to}\ 30:1.$
• Aerobic pile temperatures (hot composting): up to $160^{\circ}!F\ (\approx 71.1^{\circ}!C)$, with some sources indicating up to $150^{\circ}!F$ as a typical operating target.
• Windrow dimensions (typical): $\text{width} \approx 3' , \ \text{height} \approx 3'\text{–}5', \ \text{length} \approx 3'\text{–}300'.$
• Landfill/landfill-related data (USEPA): $63.1\ \text{million tons of food waste (2018)}$; $56\%$ to landfills; $21.6\%$ of landfill contents are food waste.
• GVSU diversion metrics: $\sim 50\%\to\sim 70\%$ waste diversion over time; $917\ \text{tons}$ composted in 2020.
• Miscellaneous metrics:
  • 2019–2020 improvements from CMU and MSU programs (WasteWise awards, zero-waste practices, portion-control strategies) as benchmarks for campus waste diversion.

Conclusion

• Composting methods vary widely in scale, efficiency, and end-product quality. A well-designed system balances oxygen, moisture, temperature, and feedstock to maximize decomposition while minimizing odors and methane production.
• Grand Valley State University has made substantial progress toward waste diversion and education but still has opportunities to close the loop between waste generation and finished compost use on campus and at SAP.
• By piloting small-scale educational systems, improving on-site composting at SAP, and leveraging external partnerships or in-house windrow systems, GVSU can enhance sustainability, demonstrate circular economy principles, and provide tangible learning opportunities for students.
• The proposed improvements draw on successful models from CMU and MSU and emphasize education, governance (Green Team), and community engagement to sustain long-term composting success.

Works Cited (Selected References)

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• Additional citations cited within the content reflect the bibliography provided in the transcript.