Although coffee is arguably one of the world’s most beloved beverages, not much thought goes into what happens to the spent coffee grounds leftover after consumers take their final sip.

Often times, the byproduct material is landfilled or composted, with little to no thought. Yet, a variety of scientists, researchers and innovators have recognized that spent coffee grounds possess several highly desirable chemical components — including sugars, proteins, lignin, potassium, nitrogen, magnesium and phosphorus, among others — that are potentially useful for some other applications that have little or nothing to do with consuming.

Follow along with GlobalSpec as we look at a few of those applications.

Clean-up

Sure, coffee grounds might prove to be an effective abrasive for cleaning the kitchen, but a team of researchers from Brazil’s Federal Technological University of Paraná suggests that spent coffee grounds could one day be used to help clean up environmental toxins.

Specifically, spent coffee grounds, according to the researchers, can be repurposed to function as an adsorbent of bentazone, which is a highly neurotoxic herbicide used in the agriculture industry.

The researchers determined that when zinc chloride was used to activate the carbon present in spent coffee grounds, the activated carbon demonstrated roughly 70% efficiency in the removal of bentazone.

Concrete

Engineers from the Royal Melbourne Institute of Technology (RMIT University) in Australia are planning to divert spent coffee grounds from landfills and simultaneously fortify concrete.

By turning roasted coffee ground waste into biochar — a carbon-enriched biomaterial produced in the combustion of biomass via a low-energy process called pyrolysis, which occurs in the complete or near absence of oxygen at 350° C — and adding it to concrete, the team reportedly strengthened concrete by 30%.

According to the researchers, coffee biochar can be used to replace a portion of the sand that goes into the manufacture of concrete — the extraction of which for the construction industry alone has had a significant impact on the environment.

Packaging film

South Dakota State University researchers are turning spent coffee grounds into biodegradable packaging film to potentially replace traditional plastic packaging film.

Making spent coffee grounds appropriate for this application is that they are readily available and contain lignocellulosic fibers, which are the ingredients necessary to manufacture films.

To create the packaging film, the team extracted lignocellulosic fibers from the spent coffee grounds and then employed a chemical modification process to make the material more appropriate for packaging.

The films developed through this process demonstrated high tensile strength, possessed antioxidant properties, blocked significant amounts of ultraviolet radiation and were biodegradable within 45 days in the soil.

Consumer products

Researchers from the University of Colorado at Boulder (CU Boulder) are using spent coffee grounds to help reduce waste from 3D printing.

Using a paste of spent coffee grounds, water and other sustainable ingredients, the team developed an approach for 3D printing a range of objects including craft jewelry, pots for plants and espresso cups, for example.

As a substitute for the thermoplastics used in 3D printing — most commonly polylactic acid, or PLA — the team turned to coffee to avoid the accumulation of PLA in landfills where the material could take up to 1,000 years to decompose.

As such, the researchers mixed water, dried coffee grounds and cellulose gum and xanthan gum, which are both common additives in food that easily degrade in a compost bin, to create a substance that resembles the consistency of peanut butter. Once dried and extruded, the substance is reportedly as tough as unreinforced concrete.

Plastic

Researchers from Australia’s Macquarie University and New Zealand’s University of Auckland are converting coffee grounds into lactic acid for producing biodegradable plastics. A synthetic pathway has been engineered for transforming mannose, which is an abundant sugar in coffee grounds, into lactic acid, which can subsequently be used in the manufacture of biodegradable plastics.

Rendering of a synthetic non-phosphorylative pathway for the conversion of spent coffee grounds into the platform chemical lactic, based on a putative mannose metabolic pathway from the archaeon T. acidophilum. Source: Macquarie UniversityRendering of a synthetic non-phosphorylative pathway for the conversion of spent coffee grounds into the platform chemical lactic, based on a putative mannose metabolic pathway from the archaeon T. acidophilum. Source: Macquarie University

Biodiesel

An international team of researchers suggests that discarded coffee grounds can serve as the foundation for a new biodiesel production method.

According to the researchers, spent coffee grounds contain nutrients that support the cultivation of Chlorella vulgaris microalgae without additional material inputs. The microalgae reportedly attach to and thrive on the surfaces of spent coffee grounds, where they build up the lipids, alkyl chains and other components that subsequently form biodiesel.

An analysis of this approach suggests that the extracted biodiesel produces minimal emissions, demonstrates suitable engine performance and meets U.S. and European specifications.

Fabric dye

Researchers from Iowa State University (ISU) have discovered a natural and environmentally friendly way to add color to clothing and other textiles using spent coffee grounds.

The ISU researchers gathered grounds from local coffee shops and dried them for three days before boiling in purified water to draw out dyes.

Those dyes were then tested on materials such as linen, silk, rayon, cotton and polyester, using an assortment of mordants, which is a substance commonly used to help dye bond to fabric. This resulted in an even greater variety of shades of brown.

Preventing diseases

Researchers from the University of Texas at El Paso have determined that caffeic-acid-based Carbon Quantum Dots (CACQDs) derived from coffee grounds could potentially protect the brain from effects of certain neurodegenerative disorders — specifically, Alzheimer’s and Parkinson’s.

According to the researchers, CACQDs proved effective when the neurodegenerative disorder was due to lifestyle and environmental factors, such as age, obesity and pesticide exposure, for instance.

The researchers explained: “Proteins misfold, and separately, free radicals are generated. Both events cause neuronal damage, injury, and demise. CQDs (CACQDs here) prevent both the misfolding of proteins and scavenge free radicals and thereby show independent mechanisms of intervention and neuronal protection.”

To contact the author of this article, email mdonlon@globalspec.com