Used coffee grounds#Knockbox

{{See also|Coffee_bean#Composition|label 1=Composition of coffee beans}}

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.{{cite journal |last1=Pérez-Burillo |first1=Sergio |last2=Cervera-Mata |first2=Ana |last3=Fernández-Arteaga |first3=Alejandro |last4=Pastoriza |first4=Silvia |last5=Rufián-Henares |first5=José Ángel |last6=Delgado |first6=Gabriel |title=Why Should We Be Concerned with the Use of Spent Coffee Grounds as an Organic Amendment of Soils? A Narrative Review |journal=Agronomy |date=November 2022 |volume=12 |issue=11 |pages=2771 |doi=10.3390/agronomy12112771 |language=en |issn=2073-4395 |doi-access=free |hdl=10481/78230 |hdl-access=free }} Used coffee grounds are rich in sugars,{{cite journal |last1=Mussatto |first1=Solange I. |last2=Carneiro |first2=Livia M. |last3=Silva |first3=João P.A. |last4=Roberto |first4=Inês C. |last5=Teixeira |first5=José A. |title=A study on chemical constituents and sugars extraction from spent coffee grounds |journal=Carbohydrate Polymers |date=January 2011 |volume=83 |issue=2 |pages=368–374 |doi=10.1016/j.carbpol.2010.07.063|hdl=1822/16744 |hdl-access=free }} which comprise about half of their weight. A further 20% is made up of proteins, and a further 20% is lignins.{{cite journal |last1=McNutt |first1=Josiah |last2=He |first2=Quan (Sophia) |title=Spent coffee grounds: A review on current utilization |journal=Journal of Industrial and Engineering Chemistry |date=March 2019 |volume=71 |pages=78–88 |doi=10.1016/j.jiec.2018.11.054|s2cid=104298839 }}

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).{{cite journal |last1=Ballesteros |first1=Lina F. |last2=Teixeira |first2=José A. |last3=Mussatto |first3=Solange I. |title=Chemical, Functional, and Structural Properties of Spent Coffee Grounds and Coffee Silverskin |journal=Food and Bioprocess Technology |date=December 2014 |volume=7 |issue=12 |pages=3493–3503 |doi=10.1007/s11947-014-1349-z |hdl=1822/31900 |s2cid=38776511 |hdl-access=free }} The quantity of caffeine remaining in used coffee grounds is around 48% of that in fresh coffee grounds.{{cite journal |last1=Campos-Vega |first1=Rocio |last2=Loarca-Piña |first2=Guadalupe |last3=Vergara-Castañeda |first3=Haydé A. |last4=Oomah |first4=B. Dave |title=Spent coffee grounds: A review on current research and future prospects |journal=Trends in Food Science & Technology |date=September 2015 |volume=45 |issue=1 |pages=24–36 |doi=10.1016/j.tifs.2015.04.012}} There are significantly less tannins in used coffee grounds than fresh coffee grounds.{{cite journal |last1=Choi |first1=Bogyoung |last2=Koh |first2=Eunmi |title=Spent coffee as a rich source of antioxidative compounds |journal=Food Science and Biotechnology |date=August 2017 |volume=26 |issue=4 |pages=921–927 |doi=10.1007/s10068-017-0144-9|pmid=30263620 |pmc=6049539 }}

On average, 1 tonne of green coffee produces approximately 650 kg of spent coffee grounds,{{cite journal |last1=Murthy |first1=Pushpa S. |last2=Madhava Naidu |first2=M. |title=Sustainable management of coffee industry by-products and value addition—A review |journal=Resources, Conservation and Recycling |date=September 2012 |volume=66 |pages=45–58 |doi=10.1016/j.resconrec.2012.06.005|bibcode=2012RCR....66...45M }} and over 15 million tonnes of spent coffee grounds are generated annually.{{cite journal |last1=Kamil |first1=Mohammed |last2=Ramadan |first2=Khalid Mustafa |last3=Awad |first3=Omar I. |last4=Ibrahim |first4=Thamir K. |last5=Inayat |first5=Abrar |last6=Ma |first6=Xiao |title=Environmental impacts of biodiesel production from waste spent coffee grounds and its implementation in a compression ignition engine |journal=Science of the Total Environment |date=July 2019 |volume=675 |pages=13–30 |doi=10.1016/j.scitotenv.2019.04.156|pmid=31026637 |s2cid=135449537 |doi-access=free |bibcode=2019ScTEn.675...13K }} In keeping with a life cycle approach to sustainability,{{cite journal |last1=Gebreeyessus |first1=Getachew Dagnew |title=Towards the sustainable and circular bioeconomy: Insights on spent coffee grounds valorization |journal=Science of the Total Environment |date=August 2022 |volume=833 |pages=155113 |doi=10.1016/j.scitotenv.2022.155113|pmid=35427619 |bibcode=2022ScTEn.83355113G |s2cid=248138300 }} 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.

File:Knockbox.jpg

A knockbox (informally known as a "bash bin", "coffee column", "slam piece" or "bang bang") is a device used to store spent espresso grounds, called a puck, after a shot of espresso has been pulled.{{Cite web |title=Best Coffee Knock Boxes |url=https://dipacci.com.au/search?type=product&q=COFFEE+KNOCK+BOX |access-date=2021-07-21 |website=Dipacci}}{{Cite web |title=Coffee machine accessories: Bang Bang |url=https://www.sunbeam.com.au/kitchen-and-home/coffee/coffee-machine-accessories/bang-bang |access-date=2021-07-21 |website=Sunbeam |language=en}} It is generally made out of stainless steel or plastic, and has a sturdy bar known as a "bash bar", against which a portafilter is tapped to release the puck. Because the espresso puck is typically very hot after extraction, knockboxes need to be sturdy. Further, they are also subject to repetitive knocking and tapping to dislodge espresso after use, and thus rubber and stainless steel are the most commonly used materials. In various coffee houses they are seen as drawers which are integral within the bar structure, or as stainless steel boxes usually located near the grinder for convenience.

It is not recommended to burn dried used coffee grounds, as they give off hazardous nitrogen oxides when burnt.

File:Worms-from-coffee-compost-pile.jpg moving about in used coffee grounds.]]

In gardens, coffee grounds may be used for composting or as a mulch{{cite web | url=http://www.huffingtonpost.com/hometalk/7-astonishing-ways-hometa_b_5632711.html | title=Don't Throw Out Your Leftover Coffee Grounds! | publisher=Huffington Post | date=4 August 2014 | access-date=25 December 2014}} 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,{{Cite book |url=https://archive.org/details/rodalebookofcomp00mart/page/86 |title=The Rodale book of composting |publisher=Rodale Press |year=1992 |isbn=978-0-87857-991-4 |editor1-last=Martin |editor1-first=Deborah L |location=Emmaus, PA |page=[https://archive.org/details/rodalebookofcomp00mart/page/86 86] |chapter=Coffee wastes |access-date=January 5, 2010 |editor2-last=Gershuny |editor2-first=Grace |editor-link2=Grace Gershuny |chapter-url=https://books.google.com/books?id=N6sx5-OM_psC&pg=PA86}} although due to acids being leached from the grounds while in use, they typically have a neutral pH, 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.{{cite journal |last1=Liu |first1=K. |last2=Price |first2=G.W. |title=Evaluation of three composting systems for the management of spent coffee grounds |journal=Bioresource Technology |date=September 2011 |volume=102 |issue=17 |pages=7966–7974 |doi=10.1016/j.biortech.2011.05.073|pmid=21704514 |bibcode=2011BiTec.102.7966L }} Used coffee grounds are particularly noted as a soil amendment.{{cite news|title=Coffee Grounds Perk up Compost Pile With Nitrogen|url=http://today.oregonstate.edu/archives/2008/jul/coffee-grounds-perk-compost-pile-nitrogen|access-date=1 April 2018|work=Life at OSU|date=10 June 2009|language=en}} Spent coffee grounds have phytotoxic properties which can be reduced through composting.{{cite journal |last1=Stylianou |first1=Marinos |last2=Agapiou |first2=Agapios |last3=Omirou |first3=Michalis |last4=Vyrides |first4=Ioannis |last5=Ioannides |first5=Ioannis M. |last6=Maratheftis |first6=Grivas |last7=Fasoula |first7=Dionysia |title=Converting environmental risks to benefits by using spent coffee grounds (SCG) as a valuable resource |journal=Environmental Science and Pollution Research |date=December 2018 |volume=25 |issue=36 |pages=35776–35790 |doi=10.1007/s11356-018-2359-6|pmid=29860699 |bibcode=2018ESPR...2535776S |s2cid=44081836 }} Gardeners have reported the use of used coffee grounds as a borer,{{cite book |title=Southern Cultivator |date=1853 |publisher=J.W. & W.S. Jones |url=https://books.google.com/books?id=xGxNAAAAYAAJ&dq=%22coffee%20grounds%22%20%2Bgarden&pg=PA156 |language=en}} slug and snail repellent,{{cite web | url=http://www.times-standard.com/lifestyle/20141224/north-coast-gardening-winter-vegetable-growing | title=NORTH COAST GARDENING: Winter vegetable growing | publisher=Eureka Times-Standard | date=24 December 2014 | access-date=25 December 2014}} but this has not yet{{when|date=June 2024}} been scientifically tested. Some commercial coffee shops run initiatives to prevent the grounds from going to waste, including Starbucks' "Grounds for your Garden" project,{{cite web|url=https://news.starbucks.com/news/starbucks-coffee-grounds-for-the-garden |title=Coffee for Your Plants? Starbucks Offers Free Coffee Grounds for Gardeners |publisher=Starbucks.com |access-date=December 13, 2015}} and community sponsored initiatives exist, such as "Ground to Ground" {{cite web|url=http://groundtoground.org/about/ |title=About Us | Coffee Grounds to Ground |date=24 May 2010 |publisher=Groundtoground.org |access-date=October 26, 2011}} or the 'Green Coffee Shop Scheme' in Cambridgeshire, UK.{{Cite web|url=https://cambridgefoodhub.org/services/green-coffee-shop-scheme/|title=Green Coffee Shop Scheme|date=2019-05-08|website=Cambridge Food Hub|language=en|access-date=2019-10-25}}

{{Main|Tasseography}}

In divination and fortune-telling, the patterns of coffee grounds are used for predictions.

Dried used coffee grounds were recommended to fill pincushions.{{cite book |url=https://books.google.com/books?id=1F1f2s4I7LIC&dq=coffee+grounds+pincushion&pg=PA347 |title=The Universal Household Assistant: A Cyclopedia of what Everyone Should Know... |date=1884 |publisher=A.L. Burt |page=347 |language=en}} Used coffee grounds have other homemade uses in wood staining, air fresheners, and body soap scrubs.

File:Oyster mushroom (Pleurotus ostreatus) mycelium on coffee grounds.JPG on coffee grounds.]]

Initiatives have succeeded using coffee grounds as a substrate for the cultivation of mushrooms (including oyster mushrooms).{{Cite web |last=Dillen |first=Nina |date=2015-06-18 |title=Zelf oesterzwammen kweken op basis van ... koffiegruis? Zo doe je dat |url=https://www.hln.be/nina-kookt/zelf-oesterzwammen-kweken-op-basis-van-koffiegruis-zo-doe-je-dat~aa08de83/ |url-status=live |archive-url=https://web.archive.org/web/20210421211510/https://www.hln.be/nina-kookt/zelf-oesterzwammen-kweken-op-basis-van-koffiegruis-zo-doe-je-dat~aa08de83/ |archive-date=2021-04-21 |access-date=2023-11-07 |website=Het Laatste Nieuws}}{{Cite web|url=https://www.permafungi.be/?lang=nl|title=PermaFungi ||date=28 March 2014 }} 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.

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.{{cite journal |last1=Yamane |first1=Koji |last2=Kono |first2=Mitsuaki |last3=Fukunaga |first3=Taiji |last4=Iwai |first4=Kazuya |last5=Sekine |first5=Rie |last6=Watanabe |first6=Yoshinori |last7=Iijima |first7=Morio |date=January 2014 |title=Field Evaluation of Coffee Grounds Application for Crop Growth Enhancement, Weed Control, and Soil Improvement |journal=Plant Production Science |volume=17 |issue=1 |pages=93–102 |doi=10.1626/pps.17.93 |s2cid=84273209 |doi-access=free|bibcode=2014PlPrS..17...93Y }}

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.{{cite journal |last1=Mussatto |first1=Solange I. |last2=Machado |first2=Ercília M. S. |last3=Martins |first3=Silvia |last4=Teixeira |first4=José A. |date=July 2011 |title=Production, Composition, and Application of Coffee and Its Industrial Residues |journal=Food and Bioprocess Technology |volume=4 |issue=5 |pages=661–672 |doi=10.1007/s11947-011-0565-z |s2cid=27800545 |hdl-access=free |hdl=1822/22361}}

Coffee grounds may be used industrially in biogas production or to treat wastewater.{{cite web|url=https://puyallup.wsu.edu/wp-content/uploads/sites/403/2015/03/coffee-grounds.pdf|title=Coffee grounds— will they perk up plants?|date=2009|publisher=Puyallup Research and Extension Center, Washington State University|work=Master Gardener|access-date=25 December 2014|last=Chalker-Scott |first=Linda}} 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.

Biodiesel may be produced from coffee grounds, either directly by extracting the oils using solvents,{{Cite journal |last1=Kondamudi |first1=Narasimharao |last2=Mohapatra |first2=Susanta K. |last3=Misra |first3=Mano |date=2008-12-24 |title=Spent Coffee Grounds as a Versatile Source of Green Energy |url=https://pubs.acs.org/doi/10.1021/jf802487s |journal=Journal of Agricultural and Food Chemistry |language=en |volume=56 |issue=24 |pages=11757–11760 |doi=10.1021/jf802487s |pmid=19053356 |issn=0021-8561|url-access=subscription }} by mixing the grounds with methane and a catalyst,{{Cite web |last=Patel |first=Prachi |date=2017-05-18 |title=A simpler route to biodiesel from used coffee grounds |url=https://www.anthropocenemagazine.org/2017/05/a-simpler-route-to-biodiesel-from-used-coffee-grounds/ |access-date=2023-10-09 |website=Anthropocene |language=en-US}} or by using the grounds to feed bio-producing algae.{{Cite web |last=Coxworth |first=Ben |date=2022-11-02 |title=Coffee grounds used to both feed and support biodiesel-producing algae |url=https://newatlas.com/science/coffee-grounds-feed-support-biodiesel-algae/ |access-date=2023-10-09 |website=New Atlas |language=en-US}}

In concrete making, 10-15% of the sand used may be replaced with used coffee grounds.{{cite news |last1=Christie |first1=Damian |date=31 October 2019 |title=From coffee to concrete: Researchers offer a new solution |work=Quarry |url=https://www.quarrymagazine.com/2019/10/31/from-coffee-to-concrete-researchers-offer-a-new-solution/}}

It has been suggested to recover caffeine from used coffee grounds for commercial applications in agrifood, cosmetic, nutraceutic or pharmaceutic industries.{{cite journal |last1=Vandeponseele |first1=Alexandre |last2=Draye |first2=Micheline |last3=Piot |first3=Christine |last4=Chatel |first4=Gregory |title=Study of Influential Parameters of the Caffeine Extraction from Spent Coffee Grounds: From Brewing Coffee Method to the Waste Treatment Conditions |journal=Clean Technologies |date=2 April 2021 |volume=3 |issue=2 |pages=335–350 |doi=10.3390/cleantechnol3020019|doi-access=free }}

In 2021, Gloucestershire-based football club Forest Green Rovers trialed a kit made from 35% used coffee grounds combined with recycled plastic.

A method of safe disposal of coffee ground waste has been tested to assist with noise management in cafés. Using coffee waste and urea resin to create sound absorbing panels, the noise generated in cafés can be reduced while coffee waste is recycled. The coffee grounds are dried, mixed with the resin, then pressed and heated.

Different particle sizes of the coffee grounds were tested. The Coffee Waste Sound Absorption (CWSA) that had the highest sound absorption coefficient was observed at 0.4g/cm3 density. While the panels were applied to the ceiling of the café, they could reduce reverberation time from 1.2 s without sound absorbing material to 0.7 s with CWSA. The sound pressure level was reduced by 7 decibels.{{cite journal |last1=Yun |first1=Beom Yeol |last2=Cho |first2=Hyun Mi |last3=Kim |first3=Young Uk |last4=Lee |first4=Sung Chan |last5=Berardi |first5=Umberto |last6=Kim |first6=Sumin |title=Circular reutilization of coffee waste for sound absorbing panels: A perspective on material recycling |journal=Environmental Research |date=1 May 2020 |volume=184 |pages=109281 |doi=10.1016/j.envres.2020.109281}}

• Ecological effects of coffee
• Sustainable coffee

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{{Coffee}}

Category:Coffee derivatives

Category:Horticulture

Category:Composting

Category:Food waste