A recipe for old leaves

Just how valuable are your garden scraps?

Every year, nearly half of our organic waste gets thrown to landfill, when all of it could be used for other things.  Local councils are slowly introducing collection schemes for people’s leaves, grass clippings, branches and plants.  They use it to make mulch, compost and soil conditioners.

But it could have a lot more potential than that.  In fact, according to this research, it could be a source of some crucial chemicals.

Step one: set out your ingredients

Plants are full of a compound called cellulose.  It’s the thing that makes their cell wall and gives them structure.  And it has a very special property: it’s chirally pure.

Chiral molecules are chemically identical, but optically different.  Since we can’t see molecules, it’s very hard to make chirally pure things in the lab.

Nature’s been doing it for millions of years, though.  We can look there for our starting materials.

These chemists began their research with levoglucosenone (LGO), which is made from cellulose extracted from green waste.  The LGO is chirally pure, like the plant matter it came from.

Step two: stir over heat

LGO is interesting, but it doesn’t have any specific uses on its own.  Fortunately, chemistry is all about seeing if you can turn something interesting into something useful.

Or, if you like, taking a cool ingredient and seeing what you can cook with it.

After treating the LGO with an enzyme, and doing a couple of follow-up reactions, these researchers found they could make a type of chemical known as an epoxide.

Epoxides are important components of a range of different things.  The epoxide made here has been used in antibiotics, pharmaceuticals and natural pesticides.  Other ways of making it use dangerous solvents and toxic by-products, but the LGO approach is much more environmentally friendly.

Step three: add flavouring (to taste)

There’s a lot you can do with a chirally pure product.  These researchers turned their epoxide into a flavour: (S)-Dairy lactone.

Dairy lactone is found in cow’s milk, and is responsible for a lot of its flavour.  When chirally pure, it tastes three times as strong, so it’s worth taking note of if you’re developing a range of food products that need cheap lactose-free flavour.  These plant-based chemicals could make a lot of money.

This sort of research is still in its infancy.  The stuff you throw in your green waste bin today is not going to be converted straight into off-the-shelf medicines.

But one day, it might.  That’s why we need to encourage these projects now.

Don’t throw your green waste to landfill.  See if you can register for a bin – and if not, have a look at your local garden waste centres.  (Those are ACT links; check your local council website if you’re interstate or overseas.)

Exactly how useful are garden scraps?  Our options are limitless.

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