Stand on our farm in Holualoa for a few minutes in the early morning and you understand what people mean when they talk about Kona coffee country. The air sits at around 1,500 feet elevation, cool and damp, laced with the smell of volcanic earth and flowering coffee trees. The Big Island's mountain slopes hold moisture from passing clouds, and the trade winds cool the afternoons just enough to slow down the coffee cherries as they ripen. It is a specific kind of place, and the soil underneath it is everything.
Every cup of coffee you have ever brewed left something behind. The grounds in your filter, the pulp stripped from the cherry on the farm, the husks that fall away during milling. These materials are not trash. They are part of a cycle that, when managed thoughtfully, feeds the very land that produces the next harvest.
Coffee waste happens at a staggering scale. Estimates put global coffee production waste at up to 15 million tons per year. That includes pulp, mucilage, spent grounds, and husks generated from farm to cup. Most of that material ends up in landfills or waterways when it could be going back into the ground. At Buddha's Cup, we have spent years thinking about how to close that loop on our own farm, and we have learned a great deal along the way.
This guide has two purposes. The first is to help you compost coffee grounds at home in a way that actually works, grounded in current science rather than gardening myths that have been passed around for decades. The second is to show you how a working Kona coffee farm approaches the same challenge at a larger scale, and why that matters for the quality of what ends up in your cup. We will cover the chemistry, the step-by-step practice, the latest research, and the specific way we connect our coffee byproducts back to our trees and our mamaki plants through what we call full-circle farming.
Some of what you read here will correct things you have heard before. The science on composting coffee grounds has matured, and a few widely held beliefs deserve a closer look. We will address those directly, because getting this right matters for your garden and for the broader conversation about what sustainable agriculture actually looks like in practice.
Why Coffee Grounds Deserve a Place in Your Compost
Before you start scooping grounds into a bin, it helps to understand what you are working with. Coffee grounds carry a specific chemical profile that makes them genuinely valuable for compost, but also capable of causing problems when used incorrectly. The good news is that the problems are avoidable once you understand the basics.
What Coffee Grounds Actually Are: The Green vs. Brown Confusion
Most people look at coffee grounds and assume they belong in the "brown" category of compost ingredients because, well, they are brown. This is one of the most common and consequential misunderstandings in home composting. Coffee grounds are, by function, a "green" material. That means they are nitrogen-rich, not carbon-rich.
In composting terms, greens are materials high in nitrogen, the nutrient that feeds the microorganisms doing the decomposition work. Browns are materials high in carbon, the structural fuel that balances the pile and prevents it from turning into a smelly, compacted mess. The classic examples of greens are fresh grass clippings, vegetable scraps, and food waste. The classic browns are dry leaves, cardboard, wood chips, and straw.
Coffee grounds have a carbon-to-nitrogen ratio of approximately 20:1. That puts them squarely in green territory, right alongside fresh grass clippings. This ratio matters enormously because a healthy compost pile needs a carbon-to-nitrogen balance of roughly 25:1 to 30:1 to decompose efficiently. Add too many greens and the pile goes anaerobic, smells like ammonia, and slows down. Add too many browns and decomposition stalls because the microorganisms run out of nitrogen to work with.
When you recognize grounds as a green material and balance them accordingly with carbon-rich browns, they become a genuinely powerful compost activator. They feed microbial populations, generate heat in the pile, and speed up the breakdown of everything around them. Used without that balance, they can compact into a dense mat that repels water and blocks airflow.
This distinction also explains why the paper filter from your morning brew belongs in the bin alongside the grounds. Filters are a brown material, adding a small but meaningful carbon contribution and physically helping to separate grounds so they do not mat together.
The Real Benefits When Grounds Are Composted Properly
When coffee grounds are composted correctly and the finished compost is worked into soil, the results are measurable and significant. Research consistently shows that soils amended with finished compost contain around 35 percent more earthworm activity than unamended soils, and they can gain one to two percent organic matter per year with consistent application. Earthworms are not just a pleasant sign of healthy soil. They aerate compaction, process nutrients into plant-available forms, and their castings contain beneficial microbial communities that support plant root health.
Coffee-amended compost also contributes to pest management in ways that surprise many gardeners. Studies from Oregon State University Extension have shown that caffeine solutions at concentrations of one to two percent cause slugs to leave treated soil. While finished compost does not deliver caffeine at those concentrations directly, the deterrent effect is worth noting for anyone managing slug pressure in a vegetable garden or ornamental bed.
Coffee grounds and tea leaves in compost have also been shown to reduce soil pH by approximately 0.5 to 1.0 units as the material breaks down. For acid-loving plants like blueberries, azaleas, and rhododendrons, this is a meaningful benefit. It is also relevant on our farm, where our volcanic soil already sits at a slightly acidic baseline and our mamaki plants thrive in those conditions.
Beyond those specific effects, finished coffee compost improves soil structure broadly. It supports drainage in dense clay soils and moisture retention in sandy or volcanic soils. On the Big Island, where our soil is derived from lava flows and can drain extremely quickly, the water retention benefit of compost-amended earth is not a minor point. It can mean the difference between a tree that pushes through dry season and one that struggles. You can read more about how we think about upcycling coffee waste in Kona as part of this broader soil-care approach.
The Warnings Science Actually Supports
Here is where we need to be honest with you, because a lot of gardening advice online treats coffee grounds as a universally benign soil amendment. The research does not support that framing.
Fresh, uncomposted coffee grounds contain polyphenols, tannins, and caffeine at concentrations that can actively harm plants and suppress the soil microorganisms you want to cultivate. Research by Linda Chalker-Scott at Washington State University, one of the most cited voices on this topic, shows that growth inhibition in plants can occur even at ground concentrations below one percent when applied directly to soil without composting first. The compounds that make coffee pleasantly bitter and stimulating in your cup are allelopathic in soil, meaning they chemically interfere with the germination and growth of other plants.
This is not a reason to avoid using coffee grounds. It is a reason to compost them first. The composting process, whether hot composting or vermicomposting, neutralizes or breaks down the problematic compounds over time. By the time compost is finished and ready to apply, those compounds are no longer present at inhibitory concentrations. The grounds have been transformed from a potential plant suppressant into a genuine soil builder.
The takeaway is straightforward: composting is not an optional step you can skip to save time. It is the step that converts coffee grounds from a risk into a resource. If you apply fresh grounds directly to your garden bed or work them into the soil without composting, you are likely doing more harm than good, regardless of what you may have read elsewhere. Everything that follows in this guide assumes that composting comes first.
How to Compost Coffee Grounds at Home: Step by Step
Now that you understand why the process matters, here is how to do it correctly at home. These steps work whether you are composting grounds from a daily French press habit or accumulating a week's worth of drip coffee filters. The principles are the same regardless of volume.
Setting Up Your Compost Bin for Coffee Grounds
Your first decision is what kind of composting setup to use. There are four main options for home composters, and coffee grounds work in all of them with minor adjustments.
An open pile or enclosed outdoor bin is the most common setup. It works well for anyone with outdoor space and produces compost in two to six months depending on how actively you manage it. A tumbler composter is a sealed rotating drum that keeps animals out and speeds up decomposition through easier turning. A countertop composter, often a Bokashi system or a small electric unit, processes food scraps including grounds in a contained space and is a good bridge to an outdoor system. A vermicomposting bin uses red wiggler worms to process organic material, produces extremely rich castings, and works well indoors or in small spaces.
For any of these systems, the layering principle applies. Coffee grounds go in as a green material and need to be balanced with carbon-rich brown materials. Good browns to pair with coffee grounds include dry fallen leaves, torn cardboard, shredded newspaper, wood chips, and dried straw. Paper coffee filters count as a brown material and can go directly into the bin alongside the grounds.
The recommended ratio for home bins is to keep coffee grounds at no more than ten to twenty percent of your bin's total volume. This is not a rigid law, but exceeding this threshold regularly leads to nitrogen overload, ammonia odor, and a pile that becomes dense and slow. If you brew a lot of coffee, alternate layers of grounds with generous layers of dry cardboard or leaves to stay in balance.
A practical tip that makes the whole process easier: keep a small countertop container near your coffee station to collect spent grounds throughout the week. A mason jar or a small lidded compost pail works well. Once it is full, take it to your outdoor bin. This prevents the common problem of letting grounds sit in a damp pile inside the house, where mold can develop quickly.
Unbleached paper filters can go in without any preparation. Bleached white filters are generally considered acceptable by most composting guides, but if you have the option, unbleached filters reduce the trace chemicals entering your compost. Reusable metal or cloth filters obviously produce no paper waste at all, which is a small but meaningful reduction in materials.
Managing Your Compost Pile for Best Results
Setting up the bin is the beginning. Active management is what turns a pile of organic material into finished compost.
Moisture is the first variable to watch. Coffee grounds hold water efficiently, which can be an asset in a dry pile but a problem in a pile that is already too wet. Your compost should feel like a wrung-out sponge: damp throughout but not dripping. If your pile feels wet and dense after adding grounds, mix in additional dry cardboard or leaves and turn the pile to introduce air. If the pile is too dry, grounds can actually help reintroduce moisture, but adding a small amount of water directly may be more efficient.
Aeration is the second critical variable. Coffee grounds compact easily when added in bulk, and a compacted pile cuts off the oxygen that aerobic decomposition depends on. Turn your pile every one to two weeks minimum. If you notice a strong ammonia smell, that is a signal that the pile has gone anaerobic, meaning it is decomposing without adequate oxygen. This produces odor, slows breakdown, and can generate compounds that harm plants. Turning and adding browns will correct this.
Temperature is your most reliable signal that the pile is working. A healthy, active compost pile reaches internal temperatures of 130 to 160 degrees Fahrenheit. At those temperatures, decomposition is fast, pathogens are killed, and the pile processes grounds and other materials efficiently. If your pile is not heating up, it usually means the carbon-to-nitrogen balance is off, the pile is too dry, or it needs more mass. Coffee grounds can help in that last case because their nitrogen content can kick-start a stalled pile.
Signs of a pile that is off-balance: an ammonia or rotten egg smell almost always signals too many greens or insufficient oxygen. Slow decomposition with no heat generation usually means too many browns or not enough moisture. Clumping or matting of grounds specifically is solved by mixing in coarser carbon material, like wood chips or shredded cardboard, and turning more frequently to break up the clumps before they dry into a crust.
Using Finished Coffee Compost in Your Garden
Finished compost is dark, crumbly, and smells like rich earth. You should not be able to identify individual pieces of food or grounds in it. If you can still see intact coffee grounds, the compost needs more time.
For vegetable garden beds, work two to four inches of finished compost into the top six to eight inches of soil before planting. For flower beds, a one to two inch top dressing worked lightly into the surface is usually sufficient. For potted plants, mix no more than twenty to thirty percent compost into your potting mix by volume, and lean toward the lower end for acid-sensitive plants.
Houseplants deserve a specific caution. Even finished coffee compost can be too much for plants that prefer neutral to alkaline conditions, such as succulents, most cacti, and plants like lavender or geraniums. If you are unsure about your houseplant's pH preferences, use the compost sparingly or skip it altogether for those particular plants. For acid-loving houseplants like gardenias or camellias, a small addition to the potting mix can be genuinely beneficial.
The plants that respond best to coffee-amended compost are those that naturally prefer slightly acidic, well-draining, organically rich soil. Blueberries, azaleas, rhododendrons, tomatoes, and peppers are reliable candidates. In Hawaii, taro and sweet potato also respond well to compost-amended volcanic soil.
The same logic that governs home-scale use of finished compost applies at farm scale, just with larger volumes and more complex logistics. That is exactly where our story at Buddha's Cup begins. If you are curious what a working Kona farm looks like in person, you are welcome to visit. We detail what to expect on our Kona coffee farm tours page.
Composting Coffee Grounds on a Working Farm: The Buddha's Cup Approach
What happens on a home scale with a jar of spent grounds becomes a genuinely complex operational challenge when you are managing a working coffee farm through harvest season. The volumes are different. The variety of organic materials is different. And the stakes, in terms of soil health across acreage rather than a backyard bed, are substantially higher.
The Waste Stream on a Kona Coffee Farm
To understand why composting matters at farm scale, you need to understand what a coffee farm actually generates as it moves from harvest to finished product. When we pick ripe coffee cherries, what we are picking is a small fruit. Inside that fruit is the seed we roast and you brew. Everything else, the outer skin, the pulp, the sticky mucilage layer, and the parchment husk, has to go somewhere.
Coffee pulp alone makes up roughly forty to sixty percent of the fresh weight of the coffee cherry. On a farm producing thousands of pounds of coffee, that is an enormous volume of organic material generated in a relatively short harvest window. Add spent grounds from any on-site brewing or cupping operations, the husks from dry-milling, and you begin to see why the global figure of up to 15 million tons of coffee production waste per year is not an exaggeration.
Coffee pulp cannot simply be discarded. It is high in sugars, organic acids, and compounds that, if washed directly into waterways, cause serious ecological damage by depleting oxygen in the water. Environmental regulations on the Big Island reflect this reality. Farmers who do not have a plan for their pulp are not just leaving value on the table. They are creating a liability.
At Buddha's Cup, we see the pulp, the husks, and the spent grounds not as a waste problem but as the raw material for our soil program. This is the core of what we mean when we talk about full-circle farming. The cherry that becomes your cup is also, through composting, the material that feeds the next generation of trees. You can also learn more about where the fermentation process happens on our farm, which is where much of the pulp separation occurs.
How We Build Farm-Scale Compost from Coffee Byproducts
Our composting approach at Buddha's Cup integrates several methods depending on the material and the season.
Coffee pulp forms the backbone of our primary compost operation. Fresh pulp is high in nitrogen and breaks down quickly, but it also generates significant heat and can become anaerobic if piled without adequate management. We layer pulp with dried coffee husks and other carbon-rich farm inputs to maintain the carbon-to-nitrogen balance at the pile level. The husks, which are the papery outer layer removed during dry processing, are an ideal brown material because they are already a byproduct of our own milling process.
One of the more promising practices we have been incorporating is biochar co-composting. Research from Ground to Ground and others working in regenerative agriculture suggests that charging biochar before soil application significantly improves its effectiveness. The recommended approach involves mixing four parts fresh coffee pulp with one part biochar, allowing the pulp's microbial activity and liquid content to inoculate the biochar with nutrients and organisms before it goes into the ground. For farms or home composters who do not have coffee pulp available, kitchen food waste can serve a similar function as a substitute activator material.
Why does this matter specifically in Hawaii? Our soil is volcanic in origin. It drains quickly, sometimes very quickly, and nutrient leaching is a real challenge. Biochar's porous structure holds water and nutrients in a way that standard compost alone does not fully address. When we charge biochar with coffee pulp compost before adding it to our beds, we are essentially building a slow-release nutrient sponge into the soil. For trees growing in lava-derived earth at 1,500 feet elevation, that water retention benefit is significant, particularly during the drier months on the leeward Kona coast.
We also use vermicomposting for a portion of our spent grounds and finer organic materials. Red wiggler worms process coffee grounds efficiently and produce castings with a remarkable diversity of beneficial microorganisms. Research comparing the microbiological characteristics of composted versus vermicomposted coffee byproducts consistently shows higher microbial diversity in vermicompost outputs, which translates to richer soil ecology when applied. The tradeoff is volume and speed: vermicomposting produces smaller quantities more slowly than hot composting. We use both methods because they serve different purposes in our soil program.
Closing the Loop: From Farm Waste to Thriving Kona Coffee Trees
The finished compost from our operation goes back to the base of our coffee trees, our mamaki plants, and other crops we grow on the farm. This is the closing of the loop, and it is not just philosophically satisfying. It has measurable agronomic consequences.
Kona coffee is exceptional in part because of how slowly it matures. The elevation, the cloud cover in the afternoons, the trade wind cooling, all of these slow the development of the cherry and allow flavor complexity to build in the bean. But that slow growth depends on consistent, stable soil nutrition. Trees that are stressed by poor soil structure or nutrient deficiency produce lower yields and less distinctive cup profiles. When we return finished compost to the base of our trees every season, we are feeding the soil ecology that makes this slow, careful growth possible without relying on synthetic fertilizers that can deliver nutrients in ways that actually accelerate growth past the optimal pace.
Healthy soil also supports our tree planting cycles. As we bring new trees online and retire older ones, the ability to establish young trees in deeply amended, biologically active soil dramatically shortens the time before those trees reach productive maturity. You can read more about how we think about sustainable tree planting timing as part of our broader farming calendar. And for a full picture of how we redirect every part of the coffee plant, our guide on upcycling coffee waste in Kona goes deeper into the specifics.
Spent Coffee Grounds vs. Fresh Grounds: Getting the Science Right
One of the persistent confusions in conversations about composting coffee grounds is the difference between spent grounds and fresh grounds. These are not the same material, and treating them as interchangeable leads to errors in both home gardening and farm management.
What "Spent" Means and Why It Changes Everything
Spent coffee grounds are what remain after brewing. Hot water has passed through the grounds and extracted the soluble compounds, including most of the caffeine, a significant portion of the chlorogenic acids, and the flavor compounds that make coffee taste the way it does. What remains is the cellular structure of the ground bean, still rich in nitrogen and organic matter, but depleted of the most problematic plant-inhibiting compounds.
Fresh, unbrewed grounds are a different animal. They contain the full concentration of caffeine, polyphenols, and tannins that the roasting process produces. Applied directly to soil, these compounds at high concentrations are genuinely allelopathic, meaning they chemically suppress the germination and growth of neighboring plants. This is not a theoretical concern. Research published in peer-reviewed journals has documented plant growth inhibition at concentrations of fresh grounds below one percent of soil volume.
Spent grounds are safer to work with than fresh grounds from a plant toxicity standpoint. But even spent grounds contain residual compounds at levels that benefit from the composting process to fully neutralize. The composting recommendation applies to both, with the understanding that spent grounds carry a lower immediate risk. If you are composting grounds from your home brewing, they are almost certainly spent grounds, and you are starting from a better baseline than someone working with fresh grounds from a roastery.
Vermicomposting vs. Hot Composting for Spent Grounds
Both major composting methods work for spent coffee grounds, but they produce different outputs and suit different situations.
Vermicomposting uses red wiggler worms to process organic material at ambient temperatures. Worms handle spent grounds efficiently, but they are sensitive to acidity. Keep grounds at no more than twenty-five to thirty percent of your worm bin's volume at any given time to avoid depressing the pH below the range where worms thrive. Worm castings produced from grounds and other food scraps are extraordinarily rich in microbial life and plant-available nutrients. They are particularly well suited for applications where soil biology is the primary goal, such as transplanting seedlings or establishing perennial plants.
Hot composting uses microbial heat generated by the decomposition process itself to break down organic material quickly. A well-managed hot pile reaches temperatures that kill pathogens and weed seeds, processes material faster than vermicomposting, and produces larger volumes of finished compost. For farm-scale operations where volume is a primary concern, hot composting is the workhorse method. The tradeoff is that the finished product, while excellent, typically has lower microbial diversity than vermicompost.
At Buddha's Cup, we do not choose between these methods. We use both. Hot composting handles our large-volume pulp and husk streams during and after harvest season. Vermicomposting handles our finer materials and supplements our soil applications with high-biology castings. The two outputs serve different purposes in our soil program, and combining them produces a more complete result than either method alone.
What the Latest Research Says
The science on composting coffee grounds has advanced significantly in the past few years. Research published in Agronomy in 2026 examined the microbiological and chemical characteristics of spent coffee grounds processed through both composting and vermicomposting. The findings confirm that both methods improve the safety and plant-availability of nutrients in spent grounds, and that vermicomposting produces measurably higher microbial diversity in the finished output, which corresponds to improved soil ecology when applied.
Research published in MDPI Sustainability in 2026 focused on circular economy applications for spent coffee grounds, examining how farms and processors can redirect ground volumes that currently go to waste into soil-building programs with documented agronomic benefits. The consistent finding across this body of research is that application rate and method matter more than any single ingredient or amendment. Getting the balance right, whether at home or at farm scale, is what determines whether coffee grounds contribute positively or cause problems.
The emerging best practice around biochar co-composting, documented through practitioner networks like Ground to Ground as recently as July 2026, adds another dimension to this picture. Using coffee pulp or food waste to charge biochar before soil application appears to substantially improve the biochar's effectiveness as a long-term soil amendment, particularly in well-draining volcanic soils like those on the Big Island. This is an area where we continue to experiment and refine our practice at Buddha's Cup.
Composting at Scale: Practical Logistics for Small and Mid-Size Farms
The principles of composting coffee grounds scale up from a home bin to a working farm, but the logistics change substantially. Volume, consistency of supply, moisture management, and carbon sourcing all require more deliberate planning when you are managing hundreds or thousands of pounds of organic material rather than a few pounds per week.
Sourcing Enough Material for a Farm-Scale Compost System
Not every farm generates enough of its own spent grounds to fuel a meaningful compost program. If your farm's coffee byproducts are primarily pulp and husks from processing rather than spent grounds from brewing, you may need to supplement your inputs from outside sources. This is where the growing coffee grounds recycling movement becomes directly relevant to farm operators.
Local cafes, hotels, and resorts generate substantial quantities of spent grounds every day, and most of them currently have no good use for the material. Establishing a consistent pickup relationship with one or more of these businesses can provide a reliable stream of nitrogen-rich green material for your compost system. In Hawaii specifically, the hospitality industry on the Big Island runs at significant volume, and the grounds generated by resort coffee service alone represent a meaningful redirectable resource.
For sourcing logistics: establish a consistent pickup schedule so the grounds do not sit too long at the source. Spent grounds that sit at room temperature begin to develop mold within a few days. Use breathable containers for transport and storage, not sealed bags or airtight buckets, because anaerobic conditions accelerate mold growth. If you cannot process grounds within two to three days of collection, store them in a cool area or refrigerate them briefly to slow mold development. When you receive them, incorporate them into the pile promptly and balance with carbon material immediately.
Building Windrow or Bin Systems That Handle High Volume
For farms with outdoor space and consistent large-volume material streams, windrow composting is the standard approach. A windrow is simply an elongated pile of compost material, typically three to five feet tall and as wide as your turning equipment can manage. Windrows are turned on a regular schedule, every one to two weeks in an active system, and the large mass generates significant internal heat that drives rapid decomposition.
In Hawaii's Kona coast microclimate, moisture management is a particular challenge for outdoor windrow systems. The leeward side of the island receives less rainfall than the windward coast, but the afternoon clouds and intermittent rain still introduce significant moisture variability. A windrow that is rained on heavily can go from ideal moisture to anaerobic in a short period. Covered bin systems, essentially windrows under a simple roof structure, provide more consistent moisture control and are worth the additional infrastructure cost for farms that can manage it.
At the farm level, finding carbon material to balance large volumes of nitrogen-rich grounds and pulp requires some creativity. Coffee husks from your own milling are an excellent starting point. Dried macadamia shells, which are generated as a byproduct of macadamia nut processing on the Big Island, are another useful brown material. Sugarcane bagasse, the fibrous material left after juice extraction, is widely available in Hawaii and breaks down well in compost. Cardboard from packaging, in bulk, is accessible from almost any retail or restaurant source and breaks down faster than wood chips. The key is to have carbon material staged and ready when nitrogen-rich inputs arrive so you can layer immediately rather than letting greens sit uncovered.
Managing moisture at scale also intersects with the drying operations on the farm. The conditions that affect compost moisture are related to the same environmental variables that govern ideal humidity levels for drying Kona beans, and understanding the microclimate of your specific farm site helps you plan both operations more effectively.
Measuring and Proving the Results
Farm-scale composting is an investment, in labor, in infrastructure, and in time. Proving that the investment is delivering agronomic returns requires measurement.
Soil testing before you begin a composting program and at regular intervals afterward is the most direct way to document results. The key metrics to track are organic matter percentage, soil pH, available nitrogen, and where possible, microbial activity indicators. Organic matter percentage is particularly telling because it moves slowly and requires consistent inputs to improve. A one to two percent gain in organic matter per year, the benchmark associated with consistent compost application, represents meaningful improvement in soil's water-holding capacity, nutrient availability, and biological health.
Timeline expectations for meaningful, visible soil improvement are one to two full growing seasons. You will not see dramatic results in the first few months. This is a regenerative process, not a quick fix. But farms that have maintained consistent compost programs for three to five years typically show soil health metrics that diverge substantially from neighboring operations still relying on synthetic inputs, with lower fertilizer costs and more resilient yields during stress events like drought or pest pressure.
Compost programs also reduce dependency on purchased synthetic inputs, and that reduction has a direct economic value. The cost savings vary by operation size and input prices, but farms that have documented their compost programs consistently report meaningful reductions in fertilizer expenditure within the first two to three years.
If you are visiting the Big Island and want to see soil-focused farming practices in action, you are welcome to join us for a farm tour. Our Kona coffee farm tours include a walk through our growing operation, and we are happy to talk soil on the trail. If you want to know exactly where to meet us, our farm tour meeting point in Holualoa page has the details.
Coffee Grounds, Mamaki Tea, and the Full-Circle Garden
Coffee is not the only thing we grow at Buddha's Cup. Our farm also cultivates mamaki, a native Hawaiian plant that has been used for centuries in traditional Hawaiian wellness practice and produces a beautiful, naturally caffeine-free herbal tea. The connection between mamaki and our composting program is more direct than you might expect.
How We Grow Mamaki Alongside Coffee at Buddha's Cup
Mamaki, known botanically as Pipturus albidus, is endemic to Hawaii. It grows naturally in the same elevation range and volcanic soil conditions that support coffee cultivation on the Big Island. This is not a coincidence. Both plants evolved or were cultivated in environments with slightly acidic, well-draining, organically rich soil, and both benefit from the same kind of soil amendments we produce through our composting program.
The pH reduction effect of coffee-amended compost, the half to one full pH unit drop