Low-temperature drying of coffee grounds for upcycling / Test cases / Coffee grounds drying, Upcycling drying

■ Low-temperature drying of coffee grounds for upcycling / KENKI DRYER / Coffee grounds dryer



Drying and Utilization of Coffee Grounds
Drying coffee grounds after coffee extraction at low temperatures reduces component changes and can be used for upcycling. In particular, the KENKI DRYER is a low-temperature indirect dryer that uses steam, which reduces component changes after drying and can be used for a variety of applications.

Importance of drying
If coffee grounds are left in a moist state, bacteria and mold can easily grow and spoil. Drying prevents this, and the use of coffee grounds as a soil conditioner, fertilizer, fuel, and material for biodegradable plastics is attracting attention.

Features of KENKI DRYER
Environmentally friendly: Steam is used as the heat source and no CO2 is generated. High drying efficiency and low steam consumption.
Low cost and low maintenance: Few wear parts, easy operation management and 24-hour unmanned operation.
Versatile: Capable of drying sticky and adhesive materials as well as organic waste and sludge with high water content.

Contribution to the environment
Drying reduces the weight of coffee grounds, which reduces the amount of industrial waste and the number of vehicles used to transport it. This also contributes to the reduction of industrial waste costs and CO2 emissions.

Patents and achievements
KENKI DRYER has obtained a total of 11 patents in Japan, Taiwan, the United States, France, Germany, the United Kingdom, Switzerland, and Canada. It is recommended for use in areas such as high moisture content organic waste dryer, sludge dryer, manure dryer, and methane digester liquid dryer.

The KENKI DRYER is an innovative and environmentally friendly drying system that enables the efficient drying and reuse of organic waste, including coffee grounds.


KENKI DRYER uses steam as the heat source for low temperature indirect drying, so there is little change in the composition of the dried material after drying, and it can be used as an upcycled product. It is possible to use it as an upcycled product.

Leaving coffee grounds in a wet state provides a suitable environment for microorganisms (bacteria and mold) to grow and cause spoilage. Coffee grounds contain high levels of organic matter, which provides a nutrient source for microorganisms and facilitates their growth. In addition, a warm environment increases microbial activity, especially at room temperature or above, which causes coffee grounds to decompose more quickly. Drying is an effective solution to these problems.

Coffee grounds are the solid material that remains after coffee beans are ground and coffee is extracted, generally a powdery substance that remains in filters and espresso machines after coffee is brewed. Coffee grounds are typically disposed of as waste, but in recent years, the drying and post-drying uses of coffee grounds have attracted considerable attention.
The dried coffee grounds can be used as soil conditioner, fertilizer, fuel, etc., and also as a material for biodegradable plastics.

KENKI DRYER, with 11 patents in 8 countries, is an indirect steam dryer, but its structure is different from other similar indirect steam dryers and is a completely unique product. Direct-fired dryers, such as burners, emit carbon dioxide from the dryer, which is against the times in terms of environmental protection and decarbonization, and drying at high temperatures means high fuel costs, rapid wear of parts, and high maintenance costs.

Although KENKI DEYER uses steam as a heat source, it does not produce more global warming gases and CO2 than KENKI DRYER during drying. In addition, the KENKI DRYER uses less steam due to its high drying heat efficiency, so you can use the steam you currently use, and if you use the excess steam, the fuel cost will not increase and the CO2 emissions will not increase compared to boilers that generate steam during the drying process. Alternatively, by installing an electric boiler, drying can be done in a decarbonized manner without producing any greenhouse gases or carbon dioxide CO2 emissions during drying.

There are no problems after start-up, and the blades of the dryer’s main body rotate at a very slow speed of 5 RPM or less, so parts wear is minimal and maintenance is easy and inexpensive. KENKI DRYER is a continuous dryer, not a batch dryer that stores and dries materials to be dried. Therefore, operation is simple and unmanned operation is possible 24 hours a day.

Drying coffee grounds to reduce their weight and the amount of waste material can contribute to environmental protection and decarbonization by reducing the cost of industrial waste, which is increasing due to the recent trucking problem in 2024, and by reducing the number of trucks transporting coffee grounds, thereby reducing carbon dioxide emissions.

KENKI DRYER, which can dry sticky and adhesive materials that cannot be dried anywhere else, is an epoch-making dryer with a total of 11 patents (2 in Japan and 9 in 7 foreign countries). Please consider KENKI DRYER for your high moisture content organic waste dryer, sludge dryer, slurry dryer, methane fermentation digested liquid dryer, and waste recycling dryer.
KENKI DRYER has been granted 11 patents in 8 countries (Japan, Taiwan, USA, France, Germany, UK, Switzerland, Canada).


■ Coffee grounds


Coffee grounds are the leftover particles of roasted coffee beans that have been brewed to extract the coffee flavor. They are essentially the used-up remains of the coffee beans after the brewing process.

Although typically thrown away, coffee grounds can actually be repurposed for a variety of uses around the house and garden. Here are some examples:

  • Fertilizer: Coffee grounds contain nitrogen, phosphorus, and potassium, which are all essential nutrients for plant growth. You can add them directly to your compost pile or sprinkle them around the base of your plants.
  • Exfoliant: The coarse texture of coffee grounds makes them a great natural exfoliant for your skin. You can mix them with some olive oil or honey to create a scrub that will help to remove dead skin cells and leave your skin feeling smooth and refreshed.
  • Deodorizer: Coffee grounds can help to absorb odors. You can place a bowl of them in your refrigerator or freezer to help eliminate unpleasant smells.
  • Cleaning: The abrasive texture of coffee grounds can also be used to clean pots and pans. Simply sprinkle them on the greasy area and scrub with a sponge.



■ Biodegradable Plastics from Coffee grounds


Creating biodegradable plastics from coffee grounds is an innovative and environmentally friendly approach to managing coffee waste. Here’s an overview of the process and benefits:


  1. Collection of Coffee Grounds: Used coffee grounds are collected from cafes, restaurants, and households.
  2. Drying and Processing: The coffee grounds are dried to remove any moisture content. They are then ground into a fine powder.
  3. Polymer Blending: The powdered coffee grounds are mixed with biodegradable polymers such as polylactic acid (PLA) or polyhydroxyalkanoates (PHA). These biodegradable polymers act as a binding agent.
  4. Molding and Shaping: The mixture is heated and molded into desired shapes using conventional plastic processing techniques such as injection molding or extrusion.
  5. Cooling and Solidification: The molded products are cooled and solidified to form biodegradable plastic items.


  1. Waste Reduction: Utilizing coffee grounds helps in reducing the amount of organic waste sent to landfills.
  2. Sustainability: Coffee grounds are a renewable resource, and creating biodegradable plastics from them reduces reliance on petroleum-based plastics.
  3. Biodegradability: Products made from coffee grounds and biodegradable polymers break down more easily in the environment, reducing plastic pollution.
  4. Cost-Effectiveness: Using coffee grounds, a byproduct of coffee consumption, can be a cost-effective raw material for producing biodegradable plastics.
  5. Enhanced Properties: Coffee grounds can enhance the properties of biodegradable plastics, such as adding natural color and improving the texture of the final product.


Biodegradable plastics made from coffee grounds can be used in various applications, including:

  • Packaging materials
  • Disposable cutlery and tableware
  • Plant pots and seedling trays
  • Cosmetic containers
  • Eco-friendly promotional products


  • Consistency: Ensuring a consistent supply of coffee grounds can be challenging.
  • Processing: Developing efficient processing methods to integrate coffee grounds with biodegradable polymers.
  • Cost: The initial cost of developing and scaling up the technology can be high.

Overall, producing biodegradable plastics from coffee grounds is a promising approach to promoting sustainability and reducing environmental impact.



■ Biodegradable Plastics


Biodegradable plastics are plastics that can be decomposed by the action of living organisms, usually microbes, into water, carbon dioxide, and biomass. Biodegradable plastics are commonly produced with renewable raw materials, micro-organisms, petrochemicals, or combinations of all three.
While the words “bioplastic” and “biodegradable plastic” are similar, they are not synonymous. Not all bioplastics (plastics derived partly or entirely from biomass) are biodegradable, and some biodegradable plastics are fully petroleum based. As more companies are keen to be seen as having “Green” credentials, solutions such as using bioplastics are being investigated and implemented more. The definition of bioplastics is still up for debate. The phrase is frequently used to refer to a wide range of diverse goods that may be biobased, biodegradable, or both. This could imply that polymers made from oil can be branded as “bioplastics” even if they have no biological components at all. However, there are many skeptics who believe that bioplastics will not solve problems as others expect.

Source:Wiki Biodegradable plastic






organic waste upcycling drying kenki dryer waste dryer 17.6.2024



kenki dryer front KENKI DRYER


■ Reasons for drying coffee grounds


Drying coffee grounds is an essential step in their reuse and repurposing for several reasons:

1. Preventing Mold and Bacterial Growth

  • Moisture Content: Fresh coffee grounds are wet and can quickly become a breeding ground for mold and bacteria if not dried properly. This can lead to unpleasant odors and health hazards.
  • Storage: Dried coffee grounds can be stored for longer periods without the risk of spoilage.

2. Reducing Weight and Volume

  • Easier Handling: Drying reduces the weight and volume of coffee grounds, making them easier to transport and handle.
  • Cost-Effective: Reducing the weight can also lower transportation costs.

3. Enhancing Processing Efficiency

  • Uniformity: Dry coffee grounds provide a more uniform material for various processing techniques, such as blending with polymers to create biodegradable plastics.
  • Grinding: Dry grounds are easier to grind into a fine powder, which is often necessary for their use in manufacturing processes.

4. Improving Quality and Consistency

  • Quality Control: Drying helps in maintaining the quality and consistency of the coffee grounds, ensuring they are suitable for the intended application.
  • Enhanced Properties: Dry grounds often have improved properties for use in products like compost, fertilizers, and biodegradable plastics.

5. Facilitating Storage and Preservation

  • Long-Term Use: Dry coffee grounds can be stored for extended periods without degrading, allowing for batch processing and use over time.
  • Versatility: They can be stockpiled and used as needed for various applications, from gardening to industrial uses.

6. Environmental Benefits

  • Reduced Waste: By drying and reusing coffee grounds, the amount of organic waste sent to landfills is reduced.
  • Resource Optimization: Maximizing the use of coffee grounds through drying and repurposing helps in conserving resources and promoting sustainability.

Drying coffee grounds is a crucial step to ensure their effective reuse, enhance their properties, and prevent issues related to spoilage and microbial growth.



■ Coffee grounds rot


When coffee grounds rot, it means they are undergoing decomposition in an uncontrolled or undesired manner, often leading to unpleasant odors, mold growth, and the potential for attracting pests. 

Causes of Coffee Grounds Rotting

  1. Excess Moisture:
    Waterlogged Conditions: If coffee grounds are stored or disposed of in a way that retains too much moisture, they can become waterlogged, creating an anaerobic (oxygen-poor) environment that slows down decomposition and promotes rotting.
  2. Lack of Aeration:
    Oxygen Deprivation: Without proper aeration, coffee grounds can become compacted, reducing oxygen flow and leading to anaerobic conditions that cause rot.
  3. Improper Storage:
    Closed Containers: Storing used coffee grounds in sealed or poorly ventilated containers can trap moisture and create conditions conducive to rotting.
  4. High Humidity and Temperature:
    Climate Factors: Warm and humid conditions accelerate microbial activity, which can quickly lead to rotting if coffee grounds are not properly managed.

Symptoms of Rotting Coffee Grounds

  1. Foul Odor:
    Sulfur Smell: Rotting coffee grounds often emit a strong, unpleasant odor resembling sulfur or rotten eggs due to the anaerobic breakdown of organic matter.
  2. Mold Growth:
    Visible Mold: Mold, often appearing as white, green, or black fuzzy growth, can develop on rotting coffee grounds.
  3. Slimy Texture:
    Decomposition Residue: Rotting coffee grounds may become slimy or sticky as the organic matter breaks down incompletely.





Compost is a mixture of ingredients used as plant fertilizer and to improve soil’s physical, chemical, and biological properties. It is commonly prepared by decomposing plant and food waste, recycling organic materials, and manure. The resulting mixture is rich in plant nutrients and beneficial organisms, such as bacteria, protozoa, nematodes, and fungi. Compost improves soil fertility in gardens, landscaping, horticulture, urban agriculture, and organic farming, reducing dependency on commercial chemical fertilizers. The benefits of compost include providing nutrients to crops as fertilizer, acting as a soil conditioner, increasing the humus or humic acid contents of the soil, and introducing beneficial microbes that help to suppress pathogens in the soil and reduce soil-borne diseases.

Source:Wiki Compost




fertilizer (American English) or fertiliser (British English) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from liming materials or other non-nutrient soil amendments. Many sources of fertilizer exist, both natural and industrially produced. For most modern agricultural practices, fertilization focuses on three main macro nutrients: nitrogen (N), phosphorus (P), and potassium (K) with occasional addition of supplements like rock flour for micronutrients. Farmers apply these fertilizers in a variety of ways: through dry or pelletized or liquid application processes, using large agricultural equipment or hand-tool methods.

Source:Wiki Fertilizer


The three primary elements of fertilizer


The three primary elements of fertilizer, essential for plant growth and commonly referred to as macronutrients in the context of plant nutrition, are:

Nitrogen (N):
Function: Promotes leaf and stem growth, as it is a crucial component of chlorophyll, the compound that plants use in photosynthesis to convert sunlight into energy. Nitrogen is also a key part of amino acids, the building blocks of proteins.
Deficiency Symptoms: Yellowing of leaves (chlorosis), stunted growth, and poor yield.

Phosphorus (P):
Function: Essential for energy transfer and storage in plants, as it is a component of ATP (adenosine triphosphate). Phosphorus also plays a vital role in root development, flowering, and seed production.
Deficiency Symptoms: Dark green or purplish leaves, delayed maturity, and poor root development.

Potassium (K):
Function: Regulates various metabolic activities in plants, including photosynthesis, protein synthesis, and water regulation. Potassium is also important for improving disease resistance and overall plant health.
Deficiency Symptoms: Leaf edges may turn yellow or brown (scorching), weak stems, and reduced resistance to drought and diseases.
Fertilizers are often labeled with an N-P-K ratio, which indicates the relative proportions of these three essential nutrients. For example, a fertilizer labeled as 10-20-10 contains 10% nitrogen, 20% phosphorus, and 10% potassium.



KENKI DRYER kenki dryer back 13.06.2024


Woman illustration coffee grounds drying kenki dryer offee grounds dryer 27.06.2024



■ Low-temperature drying of coffee grounds for upcycling / Test cases




■ Low-temperature drying of coffee grounds for upcycling / Test result


  • Material to be dry: Coffee grounds
  • Purpose of drying: Upcycling, Reducing industrial waste cost and amount
  • Moisture content: 67.1%W.B. before drying, 2.1%W.B. after drying
  • Requirements for dryer: To prevent clogging inside the dryer caused by the stickiness and adhesiveness. Automated continuous operation with no operator attended.
    Machine cost can be recovered in short term.
  • Test result: OK

coffee grounds drying kenki dryer coffee grounds dryer 27.06.2024


Waste drying

Competitive comparison


■ Self-cleaning screw / Steam Heated Twin Screw Technology
( SHTS technology )


One of the International Patented Technology that KENKI DRYER has is a self-cleaning structure called Steam Heated Twin Screw technology (SHTS technology). No matter how materials are sticky, adhesive and viscous is, they can be dried without clogging inside of the dryer because of this unique structure that no other products has.
For example, even materials stuck to the blades of one screw, blades of the other screw in the dryer’s body forcibly peels the materials off as they rotate. Since the blades rotate by peeling the material off each other, any sticky, adhesive and viscous material does not adhere to the blade, and the blades continue rotating, peeling, agitating and heating material without stopping while they carries material further. Also, since surface of blades are always renewed and kept clean, heat near the blades is not blocked and it is conducted directly into the materials.

Self-cleaning screw


■ Product characteristics

KENKI DRYER has three main characteristics. They are 1) Any materials can be dried as expected including sticky, adhesive and viscous materials and raw material slurry that no other company can deal with, 2) dried material can by recycled or utilized as raw materials because of its low-temperature drying method, and 3) there is no need to assign operator since its continuous operating system makes 24 hours unattended operation possible.



■ Drying process


The unique and original drying mechanism of KENKI DRYER is also International Patented Technology. Because 4 drying mechanisms which are crashing drying, agitation drying, circulation drying and indirect drying work simultaneously and add heat to material being dried repeatedly and continuously, inner part of the material is dried thoroughly and quality of discharged material after drying is stable. This series of drying mechanisms prevents agglomeration which causes insufficient drying from feeding process of the material into the dryer until discharging process after drying completed. Various ingenuities to conduct heat surely into inner part of the materials are exercised and stable heating and drying are proceeded continuously.



■ Heat source, Saturated steam


Even KENKI DRYER uses only saturated steam as its heat source, it is outstanding in safety and hygiene point of view with its unique drying mechanism based on combined use of conductive heat transfer method and heated air method. Since steam is a stable heat source, quality of discharged material after drying is also stable and equable. Maximum allowed steam pressure is 0.7Mpa and adjustment of steam pressure, adjustment of drying temperature in other words, can be easily done. Saturated steam is commonly used in many factories so that it can be said as a familiar and handy heat source. In comparison with drying methods using burner or hot blasts, saturated steam method is an indirect drying applying heat exchange via pipes that steam is passing through, therefore, it hardly burns the materials and is outstanding in safety and hygiene point of view.

Heat source, Steam


Please consider KENKI DRYER for drying of sticky materials, adhesive materials and materials in liquid state that no other dryer can deal with.
Initial, running and maintenance costs are low because of its simple structure based on internationally patented technology.
For sludge drying, costs of our dryers are estimated to be retrieved within 2, 3 years by reducing industrial waste disposal cost.
For raw material slurry drying, laborious works of manual operation will be decreased significantly by replacing box shaped compartment tray dryer with our dryer
In case of organic wastes drying, the waste can be recycled as fuel, fertilizer, soil conditioner and feedstuff after being dried.


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