Succinic acid is a colorless, crystalline compound used in lacquers, dyes and perfumes and as an ingredient in many consumer products, such as packaging, which might otherwise be produced with fossil fuels, and medicines.
Lin's research effort emerged from a discussion last summer between her and the Climate Group, a nonprofit organization that works with corporations and governments to develop low-carbon technologies and economies. Starbucks Hong Kong is one of the organization's members, and representatives from the Climate Group asked Lin last summer if she could experiment with converting the coffee chain's waste. In addition to collecting its leftover bakery goods, Starbucks helped fund the research by contributing a portion of proceeds made from selling eco-friendly gift sets.
Coffee grounds into fertilizer
Starbucks Hong Kong produces nearly 5,000 tons of used coffee grounds and unconsumed bakery waste each year, which is currently incinerated, composted or dumped in landfills.
"At the moment, we process around 2 kilograms of bakery waste from Starbucks every week. The yield we obtain from pastry waste is a bit higher than cheesecake," said Lin. Each kilo of stale pastry yields 0.45 kilograms of succinic acid, while cheesecake offers 0.44 kilograms.
In addition to the garbage from Starbucks, Lin converted cafeteria waste from the City University of Hong Kong.
Coffee grounds, she said, have been found to inhibit enzyme growth during fermentation, so they are no longer included in the biorefining process. But, she added, a Hong Kong-based recycling organization has been using the grounds to fertilize organically grown mushrooms that are then sold to the city's Sheraton Hotel.
The next step, Lin said, is to construct a pilot-scale facility. She said one Hong Kong-based bakery supplier produces 1 ton of waste per day that is converted into fertilizer. She said her group's process could convert that amount of waste into commercially marketable succinic acid.
"At the moment, there are companies interested in the process," she said. "We carried out a technical-economic study in which we calculated the size of the facility as processing 1 ton to succinic acid."
Lin would not disclose which companies were involved in developing the pilot facility but stated, "one of the largest waste companies in Hong Kong and China is interested."
She estimates that an announcement might be made by September and construction of the biorefinery plant could take a year to complete.
Lin and her research group announced their findings today at the 244th National Meeting & Exposition of the American Chemical Society under way in Philadelphia.
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500