Eco Cremation vs. Flame Cremation: What's the Difference? (colloquially referred to as human composting)
Choosing how to care for a loved one after death is one of the most personal decisions a family will ever make. If you’ve been researching cremation and come across the phrase “eco cremation,” you may be wondering what it means — and whether it’s meaningfully different from the conventional cremation you’re already familiar with.
The short answer: eco cremation most commonly refers to alkaline hydrolysis, also called water cremation or aquamation. Instead of fire and heat, it uses warm water and a gentle alkali solution to dissolve soft tissue over several hours. Families receive bone material similar to conventional cremation ashes — but the process uses roughly 90% less energy and produces a fraction of the carbon emissions. Flame cremation remains far more widely available, typically costs less, and is what most families picture when they hear “cremation.”
What is eco cremation and how does it compare to regular cremation?
Eco cremation most commonly refers to alkaline hydrolysis (also called water cremation or aquamation), which uses heated water and a potassium hydroxide solution over 3–8 hours to dissolve soft tissue — returning bone fragments similar to conventional cremated remains. It uses approximately 90% less energy than flame cremation and produces minimal direct emissions. Flame cremation uses fossil fuel combustion at 1,400–1,800°F and is available in all 50 states; alkaline hydrolysis is available in roughly 29 states.
- Eco cremation (alkaline hydrolysis/aquamation) uses heated water and potassium hydroxide rather than flame — consuming approximately 90% less energy than conventional cremation with no direct combustion emissions.
- Families receive 3–9 lbs of bone powder from alkaline hydrolysis — similar in volume and appearance to conventional cremated remains but typically lighter in color — so memorialization options are similar.
- Eco cremation typically costs $2,000–$4,500, more than direct flame cremation ($700–$2,500) but less than terramation ($4,950–$10,000); all options are significantly less than conventional burial.
- Alkaline hydrolysis is currently legal in approximately 29 states, making it more widely available than terramation (14 states) but less available than flame cremation (all 50 states).
- Terramation is a third eco-friendly option that goes further — transforming the body into living soil over 60–90 days and returning the body's nutrients directly to living ecosystems, not just reducing energy use.
This article explains how each process works, what you’ll receive at the end, what each costs, and where eco-friendly alternatives — including a third option called terramation — are currently available.
How Flame Cremation Works
Conventional flame cremation — the process most people are familiar with — uses direct heat to reduce the body to bone fragments. The body is placed in a cremation chamber (called a retort) and exposed to temperatures between 1,400°F and 1,800°F, sustained over approximately two to three hours. The intense heat evaporates soft tissue and organ material, leaving behind the mineral content of the bones.
After the process is complete, the bone fragments are inspected, any metal implants or surgical hardware are removed, and the remaining material is processed into a fine, sand-like consistency. This is what families receive — typically three to nine pounds of what is commonly called “ash” or “cremated remains.” The color ranges from light gray to off-white.
Flame cremation is the most widely available disposition option in the United States after conventional burial. It is offered by the vast majority of funeral homes and cremation providers across all 50 states. The national cremation rate has risen steadily and reached 63.4% in 2025, according to the National Funeral Directors Association.
Environmental impact of flame cremation
Flame cremation requires fossil fuel combustion — natural gas is the most common fuel — to sustain retort temperatures for the full duration of the process. A single flame cremation generates approximately 400 to 600 pounds of CO2 and other emissions, including small amounts of mercury from dental amalgam and particulates from the combustion process. Over the course of millions of cremations annually in the United States, this adds up to a meaningful environmental footprint.
Cost of flame cremation
Direct flame cremation — without a funeral service, viewing, or casket — typically ranges from approximately $700 to $2,500 depending on the provider and region. Cremation with a full service or funeral home package is generally higher. The FTC Funeral Rule requires providers to disclose itemized pricing in writing upon request.
How Eco Cremation (Alkaline Hydrolysis / Aquamation) Works
Alkaline hydrolysis goes by several names — eco cremation, water cremation, aquamation, and resomation are all terms for the same underlying process. Whichever name you’ve seen, the process works this way: the body is placed in a sealed stainless-steel chamber and submerged in a solution of water and an alkali — typically potassium hydroxide. The chamber is heated to approximately 200°F (95°C) at standard pressure, or up to roughly 300°F (150°C) in higher-pressure systems, and maintained for approximately six to eight hours (standard pressure) or around three hours (pressure systems). The alkaline water gently accelerates the same chemical reactions that occur during natural decomposition — but in a controlled, contained environment.
At the end of the process, the soft tissue has fully dissolved into a sterile liquid solution. The skeletal structure — the calcium phosphate mineral content of the bones — remains intact. Those bones are rinsed, dried, and processed into a fine, white powder. The color tends to be somewhat lighter than flame cremation remains, which some families find meaningful.
The liquid effluent is sterile and non-toxic. Most facilities process it as regulated wastewater, where it re-enters the water treatment system. It is not considered a hazardous material.
Environmental impact of alkaline hydrolysis
Alkaline hydrolysis uses significantly less energy than flame cremation. Studies have consistently found that water cremation consumes approximately 90% less energy than conventional flame cremation, avoiding the sustained fossil fuel combustion that makes flame cremation carbon-intensive. There are no direct combustion emissions from the process itself. The primary inputs are water, the alkali solution, and electricity to maintain temperature — the environmental impact of which varies depending on the local energy grid.
For families whose primary concern is reducing carbon emissions compared to flame cremation, alkaline hydrolysis delivers a substantial improvement.
Cost of alkaline hydrolysis
Eco cremation / alkaline hydrolysis typically costs more than direct flame cremation, reflecting the specialized equipment and lower provider availability. Pricing varies considerably by region and provider — general ranges published by funeral consumer advocacy organizations suggest $2,000 to $4,500 for direct alkaline hydrolysis without a service, though some providers charge more. As with any funeral arrangement, the FTC Funeral Rule requires itemized disclosure. Families should request a written price list before committing to any provider.
Where is eco cremation available?
Alkaline hydrolysis has been legal longer than most eco-friendly disposition options and is currently available in more states than natural organic reduction. As of early 2026, approximately 29 states have legalized alkaline hydrolysis for human remains, though operational availability is narrower — in several states the process is legal on paper but no licensed providers are currently offering it to families. The number of providers is growing, though it remains much smaller than the network of providers offering conventional flame cremation.
Side-by-Side: Eco Cremation vs. Flame Cremation
| Flame Cremation | Eco Cremation (Alkaline Hydrolysis) | |
|---|---|---|
| Process | High-heat combustion (1,400–1,800°F) | Warm water + alkali solution (200–300°F) |
| Duration | Approximately 2–3 hours | Approximately 3–8 hours |
| What families receive | 3–9 lbs of bone fragments (gray-white) | 3–9 lbs of bone fragments (lighter white) |
| Energy use | High (sustained fossil fuel combustion) | Approximately 90% less energy than flame |
| CO2 emissions | Approximately 400–600 lbs per cremation | Minimal direct combustion emissions |
| Liquid byproduct | None | Sterile effluent processed as wastewater |
| Availability | All 50 states | Approximately 22–25 states |
| Typical cost (direct) | $700–$2,500 | $2,000–$4,500 |
| Memorialization | Urn, scatter, jewelry, etc. | Same options as flame cremation |
A Third Option: Terramation
If you’re comparing eco-friendly disposition options, it’s worth knowing that alkaline hydrolysis isn’t the only alternative to flame cremation. Natural organic reduction (NOR) — the process commercially known as terramation or natural organic reduction — takes an entirely different approach.
Instead of heat or chemical reactions, terramation uses a biological process: the body is placed in a vessel along with organic materials like wood chips, straw, and flowers. Natural microbial activity, warmth, and airflow transform the body over several weeks to a few months. The result is not bone fragments but something entirely different: approximately one-half cubic yard of Regenerative Living Soil™ — nutrient-rich, finished soil that families can use to plant a tree, nourish a garden, or scatter in a meaningful landscape.
Terramation produces even lower carbon emissions than alkaline hydrolysis. Published life-cycle analyses cited by NOR providers indicate the process saves on the order of 0.84 to 1.4 metric tons of CO2 equivalent per case compared to flame cremation. And because it returns the body’s nutrients directly to living soil, many families find the environmental meaning especially resonant.
The practical tradeoff: terramation takes longer and is currently available in fewer states. As of April 2026, natural organic reduction is legal in 14 states — Washington, Colorado, Oregon, Vermont, California, New York, Nevada, Arizona, Maryland, Delaware, Minnesota, Maine, Georgia, and New Jersey — though California, New York, and New Jersey are legal but not yet fully operational.
For a detailed side-by-side comparison of terramation and alkaline hydrolysis, see our article on NOR vs. alkaline hydrolysis. For a broader look at how all eco-friendly options compare, our guide to green funeral options is a good starting point.
Which Option Is Right for Your Family?
There isn’t a single right answer — these are deeply personal decisions shaped by values, location, timeline, and what feels most meaningful. A few questions that can help:
Does it matter what you receive? Flame cremation and alkaline hydrolysis both return bone fragments, so if you’re looking for something familiar in size and how it can be used, either option works similarly. If you want to receive something that goes back to the earth as living soil — something you can plant and tend — terramation is the only option that provides that.
How much does environmental impact matter? All three options have different footprints. Flame cremation is the most carbon-intensive. Alkaline hydrolysis cuts energy use by roughly 90%. Terramation sequesters carbon in soil and returns nutrients to living ecosystems. If minimizing environmental impact is the primary goal, the options rank roughly in that order.
What’s available where you live? Flame cremation is available everywhere. Eco cremation (alkaline hydrolysis) is available in roughly half the states. Terramation is available in 14 states, with operational providers currently active in Washington, Colorado, Oregon, Vermont, Nevada, Arizona, Maryland, Delaware, Minnesota, Maine, and Georgia. Location may be the deciding practical factor. Our state-by-state guide to where NOR is legal can help you determine what’s available near you.
What does your timeline look like? Flame cremation is completed in hours and remains are typically returned within days. Alkaline hydrolysis is similarly quick — the water phase takes three to eight hours. Terramation takes several weeks to a few months. If timing is a significant consideration, this matters.
For a deeper comparison of how terramation stacks up against conventional cremation on environmental grounds, see our article on terramation vs. cremation: which is more eco-friendly?
For a complete overview of the terramation process and how it compares to all other disposition options, visit our complete guide to natural organic reduction.
Ready to explore terramation options? Contact TerraCare Partners
Find a funeral home offering terramation in your state
Sources
- National Funeral Directors Association (NFDA) — 2025 Cremation & Burial Report: national cremation rate of 63.4%. https://nfda.org/news/statistics
- Cremation Association of North America (CANA) — Alkaline hydrolysis state legalization tracking and industry data. https://www.cremationassociation.org/
- Washington State Legislature. “WAC 246-500: Handling of Human Remains — Natural Organic Reduction Standards.” https://app.leg.wa.gov/wac/default.aspx?cite=246-500
- Aquamation Industries — Public information on the alkaline hydrolysis process (aquamation), including process description and FAQ. https://www.aquamationinfo.com/
- Bio Response Solutions — Overview of the alkaline hydrolysis (bio-cremation) process and equipment context. https://www.bioresponsesolutions.com/
- U.S. Federal Trade Commission — Funeral Rule: providers are required to disclose itemized pricing in writing upon request. https://www.ftc.gov/legal-library/browse/rules/funeral-industry-practices-rule
- Washington State Legislature — SB 5001 (2019), the first law legalizing natural organic reduction in the United States. https://app.leg.wa.gov/billsummary?BillNumber=5001&Year=2019
- California Legislature — AB-351 (2022), legalizing natural organic reduction in California effective January 1, 2027. https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=202120220AB351