Used Tea Leaves and Tea Waste: Repurposed

I love to watch tightly rolled tea leaves open up as they brew!

milky jade balls

milky jade lvs

And I definitely re-brew certain loose teas, especially those with intact leaves, because they’ll continue to release flavor (along with caffeine, polyphenols, etc.).

But when we’ve wrung as much drinkable tea out of these leaves as possible, what can be done with the spent leaves? Especially when there’s a good handful of them!

With tender leaves, such as gyokuro or sencha, we can just eat them—tossed into a salad, mixed with rice, incorporated into a frittata. Voilà, no waste!

But even with unpalatable leaves, there still are options.

And on a larger scale, the agricultural waste generated by the tea industry offers myriad possibilities repurpose waste into resource.

Using Tea’s Nutrients 

Many of us recognize N-P-K as the ratio found on bags of garden and lawn fertilizers—referring to nitrogen, phosphorus, and potassium. Tea leaves are rich in these nutrients, so make one last weak brew out of those leaves; water your houseplants with the liquid and then work the leaves into garden soil.

Although the amount of tea waste generated by a household doesn’t amount to vast quantities, what about that generated during tea production? Granted, the tea dust that gathers on equipment may well find its way into teabags, but all that debris on the ground, the stems, the leaves that weren’t harvested or produced correctly, the stuff that doesn’t make the cut?

Large-scale composting of tea debris means this natural fertilizer goes to good use. A bonus: green tea waste apparently makes more iron available to those plants growing in the tea-waste-fertilized soil (Morikawa and Saigusa 2008).

All plants contain polyphenols, or micronutrients. Because tea bits and stems retain nutrients, tea waste has been used to grow mushrooms; a study in West Bengal, India, evaluated its use as food for fish and poultry.

Peter Keen, in his 2020 review of tea waste, explains that pigs in Japan, Korea, and China may be fed green tea waste because tea’s “fat-soluble nutrients are not flushed out of the body but retained so that they affect flavor-building.” (Hmm, will there be green tea bacon in our future?)

chili chocolate lvs

Using Tea’s Absorption and Adsorption Properties

We know that tea promptly stains fabric or paper, usually to our dismay, but this dyeing can mask stains on old fabrics or be used for artistic effects. At least one museum has taken advantage of this property, when Hunan Museum staff used English breakfast tea to plausible “age” a replicate of a 2100-year-old silk dress.

But tea also can adsorb toxic elements found in certain dyes, allowing them to be removed (Keen 2020)! Because dyes are present in textiles, paper, and make-up, using tea waste to remove toxins from those dyes might be a viable option across industries. Unlike absorption, in which a substance or molecules enter an interior, in adsorption a substance holds the target molecules (gas, liquid, or solute) on its surface.

A study published this past October found that in a laboratory setting, brewed tea waste efficiently removed the heavy metals lead, nickel, cadmium, and zinc from wastewater by adsorption (Çelebi, Gök, and Gök 2020). The cell walls of tea—those same cells walls that are intentionally broken by bruising or cutting when tea producers want the tea to oxidize—contain elements that react with heavy metals. Once the metals are adsorbed, they precipitate and then diffuse into the tea waste.

Keen (2020) writes that “mixed with clay, tea waste forms adsorptive membranes for removing toxic effluents from ponds that are generated as a factory byproduct” and points out that tea waste is a cheaper alternative to activated charcoal, which is currently used for this purpose.

Using waste to clean up wastewater! Think of how cost-effective this procedure could be if it works in real-life settings and could safely remove heavy metals from our water sources and prevent contaminants from ever making their way into the food chain.

CTC leaves

Tea as Fuel

Keen also notes that bio-waste can be turned into biomass fuel, bio-char, and bio-oil; bio-char, or charcoal, can be burned and used for fuel in—fittingly—the tea industry.

Spent tea waste can also be converted into usable energy, with gasification a particularly viable option, especially when that tea waste is combined with rice husks. Researchers M. S Augustine and S. J. Sekhar recently calculated that 40% tea waste is the optimal proportion.

Using Tea’s Fiber

As wood-based raw materials become harder to obtain, pulp and paper manufacturers are looking elsewhere, including at tea waste, which contains a lot of fiber. Since Turkey produces so much tea, researchers evaluated the quality of paper made with the country’s tea waste—and that waste is substantial, as in some 40,000 tons just from tea producers in the Black Sea area alone (Tutuş et al. 2015)!

In their study, Tutuş et al. found that using tea waste alone wasn’t as good as using a mixture of tea waste pulp and Turkish pine pulp because the fibers in the tea waste are too short for paper. They found that a 30-to-70 ratio of tea to the longer-fiber pine pulp made the paper sufficiently strong while remaining economical. Recommendations are that tea waste be used for short-fiber applications and that it be mixed with some type of softwood pulp to manufacture paper and cardboard (Tutuş et al. 2015).

three teas

Breaking the Tea into Its Component Parts

Besides using tea waste in its entirety, its components can also be used separately. Caffeine, of course, can be extracted and then added to medicines, energy drinks, etc. But there’s so much more!

Waste retains polyphenols, antioxidants, catechins, flavanols, cellulose, amino acid, nonsoluble proteins, caffeine, fiber, sugars, lignin, zinc, and tannic acid that make tea so rich in flavors, textures, and nutrients.  (Keen 2020)

Ongoing research extracts components from tea to evaluate how each one separately might benefit us, whether in the food, medical, manufacturing, pharmaceutical, or energy industry. Might more of these components be extracted from the waste, and then concentrated and profitably used?

Tea Waste Repurposed

Worldwide, natural resources are being depleted, are costly, and aren’t easily renewable. At the same time, our landfills and waste sites are rapidly filling. The obvious solution is to use the waste as resource, as something of value, but as ongoing studies illustrate, that requires research, innovation, and a willingness to change.

But change we must. We can start in our kitchens. And then in the initiatives we support, where and how we spend our money, and how we vote. Collectively, individual actions can eventually make a difference.

brew and leaves alt

(And brew those leaves one more time. Your houseplants will thank you.)


Sources:
–Augustine, M. A. and S. J. Sekhar, “Improvement in the Calorific Value . . . ,” Energy Fuels 33(12):12492–98. 11/12/19.
–Çelebi, H., G. Gök, and O. Gök,” Adsorption capability of brewed tea waste . . . ,” Scientific Reports 10. 10/16/20.
–Keen, P., “The many uses of tea waste,” STiR, 12/30/20.
–Morikawa, C. K. and M. Saigusa, “Recycling coffee and tea wastes to increase plant available Fe in alkaline soils,” Plant and Soil 304(1):249–55. 2008.
–Tutuş, A., Y. Kazaskeroğlu, and M. Çiçekler, M., “Evaluation of tea wastes in usage pulp and paper production,” BioResearch 10(3):5407–16. 2015.

Teas shown are China Milky Jade, Chili Chocolate, and O’Sullivan’s Favorite from TeaHaus.

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