What we throw away
The coffee cherry delivers only 1 to 5% of its mass to the cup. Skin, pulp, mucilage, parchment, silverskin, washing water, spent coffee grounds, capsule: each stage of the chain sets aside a material that the trade has treated as waste for three centuries, whereas Yemen drank the husk of it and the chemists of 1922 were already proposing its use as fertilizer and alcohol. This plate follows each by-product from the cherry to the cup, with its composition, its toxicity, its recovery routes, their players, their real scales and their obstacles, after Ukers (1922), La Roque (1732), chemistry and agronomy reviews, Ethiopian and Colombian field studies on washing water, the Beyond Coffee report of the International Coffee Organization (2024), European regulatory texts and the Livre café.
The 15 sections of this plate
Each section has its own page. The first sentence says what you will find there.
- 01The mass balance, from cherry to drunk beanA ripe cherry weighs 1.5 to 2 g. According to the ratio given by René Coste and still in use, it takes 5 to 7 kg of arabica cherries for one kilo of marketable coffee, 5 kg for canephora and 12…
- 02Three centuries of drinking the husk: qishr, kisher and Sultana's coffeeThe part of the cherry that the West threw away for a century and a half, the region that made coffee a drink never stopped drinking.
- 031922: pulp as fertilizer, alcohol and fuelUkers's chemistry chapter shows that putting the pulp to use is nothing new.
- 04Pulp: composition, toxicity and what can be done with itThe pulp (exocarp and mesocarp) comes out wet, sugary, all at once during the weeks of harvest, and begins to ferment the same day; it is the biggest item and the hardest to handle.
- 05Cascara, from waste to “novel food”The Spanish word cáscara means the rind or husk.
- 06Mucilage and washing waterUnder the pulp, the mucilage: about 22 kg per 100 kg of cherries, a layer of pectins and sugars that the washed process dissolves by fermentation then rinses with plenty of water, that the dry process keeps and that the honey processes keep in part (see the processing).
- 07Treating the water: lagooning, wetlands, biodigesters, BECOLSUBFour families of responses exist, from the most rustic to the most radical.
- 08Parchment and husks: fuel, biochar, paper, cupUnder the mucilage, the endocarp, the hard straw-colored envelope that gives parchment coffee its name; 35 to 39% of the weight of the dried cherry, removed at hulling just before export.
- 09Silverskin: the smallest item, the most industrializedUnder the parchment, stuck to the seed, is the seed coat, thinner than an onion skin.
- 10Spent coffee grounds: composition, phytotoxicity, household usesThe spent coffee grounds no longer belong to the cherry but to this story.
- 11Spent coffee grounds in cities: biofuel, logs, cosmetics, activated carbonThe story of Bio-bean sums up the difficulty.
- 12CapsulesThe capsule adds a waste the cherry had not foreseen:
- 13The carbon footprint of a cupMark Maslin and Carmen Nab (University College London) quantify the footprint of coffee per kilo of green coffee.
- 14From line to circle: what blocks and what worksIf all this is known, quantified, tested and sometimes commercialized, why does 86% of the weight of the world harvest still end up in piles?
- 15Today (2023-2026)The deposit is growing, and several figures are needed to pin it down, because none covers exactly the same scope.
Elsewhere on the site, the passages that deal with the same things as this page. Computed from the text, not picked by hand.