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Used coffee grounds is the result of brewing coffee, and are the final product after preparation of coffee. Despite having several highly-desirable chemical components, used coffee grounds are generally regarded as waste, and they are usually thrown away or composted. As of 2019, it was estimated that over 15 million tonnes of spent coffee grounds are generated annually. Due to this quantity of waste and the chemical properties of used coffee grounds, they have several potential uses.
In the late 19th century, used coffee grounds were used to adulterate pure coffee. [1]
Most used coffee grounds are similar in chemical composition, although coffee grounds used to make instant coffee have fewer chemicals in them due to a more extensive extraction process. [2] Used coffee grounds are rich in sugars, [3] which comprise about half of their weight. A further 20% is made up of proteins, and a further 20% is lignins. [4] The dry coffee grounds contain significant amounts of potassium (11.7 g/kg), nitrogen (27.9 g/kg), magnesium (1.9 g/kg), and phosphorus (1.8 g/kg). [5] The quantity of caffeine remaining in used coffee grounds is around 48% of that in fresh coffee grounds. [6] There are significantly less tannins in used coffee grounds than fresh coffee grounds. [7]
On average, 1 tonne of green coffee produces approximately 650 kg of spent coffee grounds, [8] and over 15 million tonnes of spent coffee grounds are generated annually. [9] In keeping with a life cycle approach to sustainability, [10] this large quantity of waste requires waste management plans. Due to the amount of spent coffee grounds generated and the chemical properties of spent coffee grounds, the usage of spent coffee grounds is avidly investigated. [6]
It is not recommended to burn dried used coffee grounds, as they give off hazardous nitrogen oxides when burnt. [4]
In gardens, coffee grounds may be used for composting or as a mulch [11] as they are known to slowly release nitrogen into the soil. They are said to be especially appreciated by worms and acid-loving plants such as blueberries, [12] although due to acids being leached from the grounds while in use, they typically have a neutral pH, [13] and red wiggler growth and survival has been experimentally tested and found to be reduced in treatments using used coffee grounds as the primary feedstock for the worms. [14] Used coffee grounds are particularly noted as a soil amendment. [13] Spent coffee grounds have phytotoxic properties which can be reduced through composting. [15] Gardeners have reported the use of used coffee grounds as a borer, [16] slug and snail repellent, [11] [17] but this has not yet[ when? ] been scientifically tested. [18] Some commercial coffee shops run initiatives to prevent the grounds from going to waste, including Starbucks' "Grounds for your Garden" project, [19] and community sponsored initiatives exist, such as "Ground to Ground" [20] or the 'Green Coffee Shop Scheme' in Cambridgeshire, UK. [21]
In divination and fortune-telling, the patterns of coffee grounds are used for predictions.
Dried used coffee grounds were recommended to fill pincushions. [22] Used coffee grounds have other homemade uses in wood staining, air fresheners, and body soap scrubs. [11]
Initiatives have succeeded using coffee grounds as a substrate for the cultivation of mushrooms (including oyster mushrooms). [23] [24] The use of spent coffee grounds in this application has the advantage of the used coffee grounds needing no pre-treatment to be usable as a mushroom substrate. [6]
Application of 10 kg used coffee grounds per square metre has been suggested as part of a crop rotation system, where for the first six months, the field is allowed to lie fallow with a layer of coffee grounds on it suppressing weed growth, then the coffee grounds are plowed in and legumes are grown, which fix their own nitrogen. Application of an equal amount of horse manure at the same time as the coffee grounds has been shown to nearly eliminate negative effects of fresh used coffee grounds. [25]
It has been proposed to use spent coffee grounds to feed ruminants, pigs, chickens and rabbits, but the high lignin content makes this an undesirable use. [26]
Coffee grounds may be used industrially in biogas production or to treat wastewater. [18] Bioethanol may also be produced from the sugar content of spent coffee grounds, after it is defatted as a pre-treatment, it is typically hydrolysed by dilute acid. [4]
Biodiesel may be produced from coffee grounds, either directly by extracting the oils using solvents, [27] by mixing the grounds with methane and a catalyst, [28] or by using the grounds to feed bio-producing algae. [29]
In concrete making, 10-15% of the sand used may be replaced with used coffee grounds. [30]
It has been suggested to recover caffeine from used coffee grounds for commercial applications in agrifood, cosmetic, nutraceutic or pharmaceutic industries. [31]
In 2021, Gloucestershire-based football club Forest Green Rovers trialed a kit made from 35% used coffee grounds combined with recycled plastic.
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.
Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class. It is mainly used as a eugeroic (wakefulness promoter) or as a mild cognitive enhancer to increase alertness and attentional performance. Caffeine acts by blocking binding of adenosine to the adenosine A1 receptor, which enhances release of the neurotransmitter acetylcholine. Caffeine has a three-dimensional structure similar to that of adenosine, which allows it to bind and block its receptors. Caffeine also increases cyclic AMP levels through nonselective inhibition of phosphodiesterase.
A fertilizer or fertiliser 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.
Mycelium is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are found in and on soil and many other substrates. A typical single spore germinates into a monokaryotic mycelium, which cannot reproduce sexually; when two compatible monokaryotic mycelia join and form a dikaryotic mycelium, that mycelium may form fruiting bodies such as mushrooms. A mycelium may be minute, forming a colony that is too small to see, or may grow to span thousands of acres as in Armillaria.
Spent mushroom compost is the residual compost waste generated by the mushroom production industry.
Instant coffee is a beverage derived from brewed coffee beans that enables people to quickly prepare hot coffee by adding hot water or milk to coffee solids in powdered or crystallized form and stirring. The product was first invented in Invercargill, the largest city in Southland, New Zealand, in 1890. Instant coffee solids refers to the dehydrated and packaged solids available at retail used to make instant coffee. Instant coffee solids are commercially prepared by either freeze-drying or spray drying, after which it can be rehydrated. Instant coffee in a concentrated liquid form, as a beverage, is also manufactured.
A biorefinery is a refinery that converts biomass to energy and other beneficial byproducts. The International Energy Agency Bioenergy Task 42 defined biorefining as "the sustainable processing of biomass into a spectrum of bio-based products and bioenergy ". As refineries, biorefineries can provide multiple chemicals by fractioning an initial raw material (biomass) into multiple intermediates that can be further converted into value-added products. Each refining phase is also referred to as a "cascading phase". The use of biomass as feedstock can provide a benefit by reducing the impacts on the environment, as lower pollutants emissions and reduction in the emissions of hazard products. In addition, biorefineries are intended to achieve the following goals:
A soil conditioner is a product which is added to soil to improve the soil’s physical qualities, usually its fertility and sometimes its mechanics. In general usage, the term "soil conditioner" is often thought of as a subset of the category soil amendments, which more often is understood to include a wide range of fertilizers and non-organic materials. In the context of construction soil conditioning is also called soil stabilization.
Bioplastics are plastic materials produced from renewable biomass sources, such as vegetable fats and oils, corn starch, straw, woodchips, sawdust, recycled food waste, etc. Some bioplastics are obtained by processing directly from natural biopolymers including polysaccharides and proteins, while others are chemically synthesised from sugar derivatives and lipids from either plants or animals, or biologically generated by fermentation of sugars or lipids. In contrast, common plastics, such as fossil-fuel plastics are derived from petroleum or natural gas.
Green waste, also known as "biological waste", is any organic waste that can be composted. It is most usually composed of refuse from gardens such as grass clippings or leaves, and domestic or industrial kitchen wastes. Green waste does not include things such as dried leaves, pine straw, or hay. Such materials are rich in carbon and considered "brown wastes," while green wastes contain high concentrations of nitrogen. Green waste can be used to increase the efficiency of many composting operations and can be added to soil to sustain local nutrient cycling.
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.
Digestate is the material remaining after the anaerobic digestion of a biodegradable feedstock. Anaerobic digestion produces two main products: digestate and biogas. Digestate is produced both by acidogenesis and methanogenesis and each has different characteristics. These characteristics stem from the original feedstock source as well as the processes themselves.
Algae fuel, algal biofuel, or algal oil is an alternative to liquid fossil fuels that uses algae as its source of energy-rich oils. Also, algae fuels are an alternative to commonly known biofuel sources, such as corn and sugarcane. When made from seaweed (macroalgae) it can be known as seaweed fuel or seaweed oil.
Agricultural pollution refers to biotic and abiotic byproducts of farming practices that result in contamination or degradation of the environment and surrounding ecosystems, and/or cause injury to humans and their economic interests. The pollution may come from a variety of sources, ranging from point source water pollution to more diffuse, landscape-level causes, also known as non-point source pollution and air pollution. Once in the environment these pollutants can have both direct effects in surrounding ecosystems, i.e. killing local wildlife or contaminating drinking water, and downstream effects such as dead zones caused by agricultural runoff is concentrated in large water bodies.
Wood-free paper is paper created exclusively from chemical pulp rather than mechanical pulp. Chemical pulp is normally made from pulpwood, but is not considered wood as most of the lignin is removed and separated from the cellulose fibers during processing, whereas mechanical pulp retains most of its wood components and can therefore still be described as wood. Wood-free paper is not as susceptible to yellowing as paper containing mechanical pulp. Wood-free paper offers several environmental and economic benefits, including reduced deforestation, decreased energy consumption, and improved waste management. The term Wood-free paper can be rather misleading or confusing for someone unfamiliar with the papermaking process because paper is normally made from wood pulp derived from trees and shrubs. However, wood free paper does not mean that the paper in question is not made from wood pulp but it means that the lignin in the wood fiber has been removed by a chemical process.
Agricultural microbiology is a branch of microbiology dealing with plant-associated microbes and plant and animal diseases. It also deals with the microbiology of soil fertility, such as microbial degradation of organic matter and soil nutrient transformations. The primary goal of agricultural microbiology is to comprehensively explore the interactions between beneficial microorganisms like bacteria and fungi with crops. It also deals with the microbiology of soil fertility, such as microbial degradation of organic matter and soil nutrient transformations.
Cold brew coffee, also called cold water extraction or cold pressing, is the process of steeping coffee grounds in water at cool temperatures for an extended period. Coarse-ground beans are soaked in water for about 12 to 24 hours.
Reuse of human excreta is the safe, beneficial use of treated human excreta after applying suitable treatment steps and risk management approaches that are customized for the intended reuse application. Beneficial uses of the treated excreta may focus on using the plant-available nutrients that are contained in the treated excreta. They may also make use of the organic matter and energy contained in the excreta. To a lesser extent, reuse of the excreta's water content might also take place, although this is better known as water reclamation from municipal wastewater. The intended reuse applications for the nutrient content may include: soil conditioner or fertilizer in agriculture or horticultural activities. Other reuse applications, which focus more on the organic matter content of the excreta, include use as a fuel source or as an energy source in the form of biogas.
Brewer's spent grain (BSG) or draff is a food waste that is a byproduct of the brewing industry that makes up 85 percent of brewing waste. BSG is obtained as a mostly solid residue after wort production in the brewing process. The product is initially wet, with a short shelf-life, but can be dried and processed in various ways to preserve it.
Seaweed fertiliser is organic fertilizer made from seaweed that is used in agriculture to increase soil fertility and plant growth. The use of seaweed fertilizer dates back to antiquity and has a broad array of benefits for soils. Seaweed fertilizer can be applied in a number of different forms, including refined liquid extracts and dried, pulverized organic material. Through its composition of various bioactive molecules, seaweed functions as a strong soil conditioner, bio-remediator, and biological pest control, with each seaweed phylum offering various benefits to soil and crop health. These benefits can include increased tolerance to abiotic stressors, improved soil texture and water retention, and reduced occurrence of diseases.