What Is Mill 'Food Grounds'? How Mill Processes Food Waste

Quick Answer: Mill is a food recycler — the company's own term — not a composter. Mill uses heat and grinding to dehydrate food waste overnight into a dry, coffee grounds-like material called "Food Grounds." Mill does not describe Food Grounds as compost, and the company's service model sends collected Food Grounds to farms for use as animal feed rather than garden compost. This guide explains how Mill works, what Food Grounds is, how to use it, and how it differs from finished compost.

Table of Contents

• How Mill Works
• What Are Food Grounds?
• Why Mill Calls Itself a "Food Recycler," Not a Composter
• Can You Use Food Grounds in Your Garden?
• What Finished Compost Does That Food Grounds Doesn't
• Mill vs Reencle: Two Different Approaches
• Price and Ownership Comparison
• Frequently Asked Questions
• References

How Mill Works

Mill is a countertop food waste appliance that connects to an app and uses an overnight dehydration process to reduce food scraps.

According to Mill's product documentation:

• The device runs overnight, using heat and mechanical turning to dehydrate food waste
• The process reduces food waste by up to 80% by weight through moisture removal
• The resulting material — Mill calls it "Food Grounds" — is a dry, granular, coffee grounds-like substance
• Mill's subscription service includes collection of Food Grounds via mail, which Mill then sends to farms for use as chicken feed supplement

Mill's service model is built around this end-to-end loop: kitchen scraps → Food Grounds → farm animal feed → food back to consumers. It's a food recycling system in the literal sense — the nutrition from food waste is recaptured and re-enters the food system.

Mill is transparent about this positioning. Their marketing consistently uses "food recycler" language, and their website explains the chicken feed end-use directly.

What Are Food Grounds?

Mill describes Food Grounds as:

• Dry, granular material resembling coffee grounds in texture
• Reduced food waste — the original food's volume and weight are significantly reduced through moisture removal
• Appropriate for chicken feed (Mill's primary end-use application)
• Not compost — Mill does not describe Food Grounds as compost anywhere in their standard product documentation

The dehydration process that creates Food Grounds works by removing water from food scraps at elevated temperature. Because moisture is the primary mechanism of biological decomposition, removing moisture halts microbial activity.

What remains in Food Grounds: the dry organic components of the original food — carbohydrates, proteins, fats — in reduced-volume, desiccated form. The nutritional content of the original food is largely preserved, which is what makes it suitable for animal feed applications.

What is not present in Food Grounds: the biological transformation that defines finished compost. Organic molecules have not been metabolized by microorganisms into humus. The material is dehydrated food, not decomposed food.

Why Mill Calls Itself a "Food Recycler," Not a Composter

Mill's choice of "food recycler" terminology is intentional and accurate to what the product does.

Composting, per the United States Composting Council's definition, requires controlled aerobic biological decomposition that results in a stabilized material that improves soil properties. This involves a specific thermophilic phase driven by microbial metabolism.

Mill's process — overnight heat dehydration — produces a different type of output that serves a different purpose. Mill's chosen end-use (animal feed supplement) makes the distinction practical: Food Grounds retains the caloric and protein content of the original food, which is valuable for feed but isn't the goal of composting.

Mill's positioning is clear in their own materials. Their website describes the device as "a new kitchen appliance that's part of a food recycling system." The word "compost" is notably absent from their core positioning.

This isn't a gap or an omission to criticize — it accurately describes what Mill does. Understanding Mill as a food recycler rather than a composter helps set appropriate expectations for the product.

Can You Use Food Grounds in Your Garden?

Mill's primary use case for Food Grounds is their mail-back collection service for animal feed. However, Mill also acknowledges that Food Grounds can be used in home gardens.

Mill's garden application guidance:

Mill notes that Food Grounds can be worked into garden soil, but with important caveats:

• Food Grounds should be mixed into soil rather than applied on the surface
• Because Food Grounds is not finished compost, it continues to decompose in soil after application
• During active decomposition in soil, microorganisms processing the Food Grounds can temporarily draw down available soil nitrogen (called "nitrogen immobilization"), which may affect plant growth
• Mill recommends diluting Food Grounds with soil rather than applying concentrated amounts

These guidelines are consistent with the nature of the material: it's partially processed organic matter that will continue decomposing after soil incorporation. Gardeners familiar with using fresh wood chips, raw manure, or other "not-yet-composted" organic materials will recognize this pattern — the material is beneficial over time but requires care in application.

Bottom line: Food Grounds can be used in gardens when applied thoughtfully per Mill's guidelines. The main difference from finished compost is that it requires continued decomposition in soil, appropriate dilution, and some lead time before the material is fully integrated.

What Finished Compost Does That Food Grounds Doesn't

Finished compost and Food Grounds serve different purposes and have different soil effects because they are different materials.

Finished compost:

• Has already completed biological decomposition — microorganisms have metabolized the organic molecules
• Is biochemically stable — it won't draw down soil nitrogen because it's no longer actively decomposing
• Contains humic acids and humus — complex organic polymers that improve soil aggregation, water retention, and long-term fertility
• Can be applied directly to planting areas including seed starting and around plant roots
• Contains diverse beneficial microorganisms that inoculate soil and support plant health

Mill Food Grounds:

• Is not yet stable — decomposition continues after soil incorporation
• Can create temporary nitrogen immobilization if applied in large amounts near plants
• Does not yet contain humus compounds — these form through the decomposition that occurs after soil incorporation
• Requires dilution and buffer time before intensive planting
• Primary designed end-use: animal feed, not soil amendment

Both can be beneficial in a garden context when used appropriately. The distinction is that finished compost can be applied directly as a ready-to-use soil conditioner, while Food Grounds functions more like a raw organic input that will become beneficial after it continues breaking down in soil.

Mill vs Reencle: Two Different Approaches

Mill and Reencle are built on different philosophies about what should happen to food waste:

Mill's approach: Capture the nutritional value of food waste, dehydrate it to reduce volume, and return it to the food system as animal feed. It's a recycling model — food in, food (indirectly) out.

Reencle's approach: Biologically decompose food waste using a maintained microbial culture, producing finished compost that returns organic matter and microbial life to garden soil. It's a composting model — food in, soil amendment out.

Price and Ownership Comparison

Mill's total cost of ownership includes the device and the ongoing subscription for their collection service.

Mill:

• Device: approximately $999–$1,299 (pricing has varied)
• Subscription: approximately $33/month for mail-back collection service
• Without subscription: You keep Food Grounds for home garden use, but collection service is the primary designed model
• 3-year estimated cost: $999–$1,299 (device) + ~$1,188 (subscription) = ~$2,200–$2,500

Reencle:

• Device: $499
• Ongoing cost: filter/microbe replacement approximately $20–40/year
• No subscription required
• 3-year estimated cost: $499 (device) + ~$90 (3 years of filters) = ~$590

The pricing difference is substantial. The appropriate comparison depends on what each product is being evaluated for — Mill's value is partially in its collection service and the food-system recycling model, while Reencle's value is in continuous home composting.

Frequently Asked Questions

Q: Is Mill a composter?

A: Mill does not describe itself as a composter. The company consistently uses "food recycler" terminology. Mill's process (heat dehydration) and output (Food Grounds) are different from biological composting, and Mill's primary designed use for the output is animal feed rather than garden compost. Mill is accurate in its own positioning.

Q: Can I use Mill Food Grounds as fertilizer?

A: Mill Food Grounds can be incorporated into garden soil and will release nutrients as it continues decomposing. However, Mill recommends diluting it and allowing decomposition time in soil before intensive planting. It is not a ready-to-apply fertilizer or finished compost; it's more accurately described as a raw organic input that becomes beneficial after continued decomposition in soil.

Q: Is Mill worth it without the subscription?

A: Without the subscription, you retain Food Grounds for home garden use. The device still functions, but the mail-back collection service — which is a core part of Mill's value proposition and food-system impact model — is unavailable. Whether the device alone at its price point serves your needs depends on how you plan to use the output.

Q: I'm deciding between Mill and Reencle — what are the main differences?

A: The main differences are the process, output type, and cost model. Mill dehydrates food waste into Food Grounds for animal feed (or home garden use with dilution). Reencle biologically composts food waste into finished compost for direct garden application. Mill has a higher device and ongoing cost including subscription; Reencle has a lower device cost and no subscription. Both accept most food waste including meat and dairy.

Q: Does Mill's Food Grounds improve soil long-term?

A: Over time, as Food Grounds decomposes in soil, it does contribute organic matter and nutrients. The long-term effect on soil organic matter, microbial populations, and structure depends on application rate, soil conditions, and what else is being added. Finished compost, which has completed biological transformation, has a more directly documentable soil biology benefit because it contains humus and active microbial populations upon application.

References

1. United States Composting Council. What Is Compost? https://www.compostingcouncil.org/

2. U.S. Environmental Protection Agency. Composting At Home. https://www.epa.gov/recycle/composting-home

3. Mill. How Mill Works. https://mill.com/ (product documentation, accessed 2026)

4. Magdoff, F., & Van Es, H. (2009). Building Soils for Better Crops: Sustainable Soil Management (3rd ed.). Sustainable Agriculture Research & Education (SARE).

5. Diacono, M., & Montemurro, F. (2010). Long-term effects of organic amendments on soil fertility. Agronomy for Sustainable Development, 30(2), 401–422.

6. Rynk, R. (Ed.). (1992). On-Farm Composting Handbook. Northeast Regional Agricultural Engineering Service (NRAES-54). Cornell University.