Page 14 - Science Focus (issue 15)
P. 14
Food waste generally refers to acid, which currently comes
uneaten, discarded food. It seems that no from petroleum, can also
matter how hard we try to make full use of be used to manufacture
food and avoid generating food waste with lunchboxes, wrapping bags and
our personal effort, municipal food waste is eating utensils. In the near future, we can
still unavoidable. According to the latest data synthesize polylactic acid from food waste
from the Environmental Protection Department to make all these products, reducing our
in 2017 [1], the solid waste disposed in the landfills dependence on petroleum.
in Hong Kong weighs up to 10 733 tonnes daily, of
which nearly 34% is food waste, weighing up to Apart from manufacturing thread, food
3 662 tonnes. With the amount of food waste on the waste can be used to produce dyes as well. The
rise, there is an urgent need for novel solutions to campaign of using food waste in cloth dyeing
alleviate this problem. was started by a food designer, Eric Cheung,
a graduate from the Open University of Hong
There are many recent discoveries on new uses Kong. Eric and a group of teenagers have been
of food waste, including textiles manufacturing picking the leftover vegetables from piles of
and dyeing. This also provides innovations to green waste, recycling vegetables discarded by the
fashion, which is no longer limited to organic cotton greengrocers and coffee grounds from cafes.
or organic silk. Dr. Carol Lin, an assistant professor With the food waste as dyes, the teenagers have
from the School of Energy and Environment of the produced colorful fabrics using a traditional tie-
City University of Hong Kong, leads her team in the dye technique. In fact, the vegetables that they
research on synthesizing textile by extraction and collect from the greengrocers are the ones with
conversion of useful materials in food waste [2]. only minor flaws or cracks on the surface. Eric
thinks that it would be a waste if they are sent
Firstly, the team collects food waste from fast to the landfills and therefore decided to receive
food shops, supermarkets and bakeries. They then them. Eric’s group would then extract the pigments
1
apply fungal hydrolysis to the collected food from the food waste by a series of steps, including
waste, through which the food is broken down sterilizing, air-drying and squeezing the food. The
into glucose, free amino nitrogen, color of the fabric can be adjusted by altering
vitamins and minerals. This step also different parameters of the dyeing process,
transforms solid food waste into liquid including duration and pH. For instance, the purple
which will give a brownish yellow cabbage turns into blue upon addition of baking
color after precipitation. soda; but turns into dark pink upon addition of
Next, the team makes use of bacterial vinegar. Therefore, food waste can indeed be used
2
fermentation to produce lactic acid from to create a rich color palette.
food molecules, and further generate polylactic Power generation is no longer the only way to
acid (PLA) through polymerization . With the fully utilize food waste. In the future, you may find
3
technique of melt spinning, lactic acid fiber can models wearing “food waste” down the catwalk.
be obtained. With additional steps, the brownish If scientists succeed in scaling up the production
yellow thread can be transformed into white, fine of textile from food waste, it should partially relieve
thread. The team succeeded in turning 100 grams the pressure on landfills. This would also bring good
of food waste into 10 grams of lactic acid fiber news to the textile industry and environmentalists.
within a week.
This discovery is exciting for several reasons. First 1 Hydrolysis: The chemical breakdown of some more
of all, this process can reduce the solid waste being complicated, larger molecules to simpler, smaller
sent to the landfills. Besides, this method has a low molecules. Water is required in the reaction.
production cost as food waste is readily available. 2 Fermentation: The catabolic reaction that breaks
At the same time, the equipment involved is neither down larger molecules into smaller molecules by
microorganisms.
complicated nor expensive, so it can provide 3 Polymerization: The process of connecting many
environmentally friendly, economical raw materials monomers to form larger polymers which consist
to the textile industry. On the other hand, polylactic of the monomers as repeating units.
