Science AMA Series: We are researchers from the University of South
Africa and we’re putting greenhouse gases directly into actual
greenhouses; we thereby capture carbon emissions, reduce water
consumption and increase crop yield. Ask Us Anything!
Abstract
Water scarcity poses a severe threat to all humankind, with rapidly
growing demand pressuring already-constrained water resources, many of
which are unsustainable. Figuring out where our water ends up is
therefore a crucial step toward finding ways to use it more efficiently
and try to ensure that we, as a species, are still around a few
generations from now. Dr Neil Stacey is a young researcher previously
known for best known for patented advances in bio-fuels production
technology. In late 2016 he set out to use chemical engineering modeling
methods to examine water usage in agriculture, which comprises 70% of
all of mankind’s water consumption. Professor Diane Hildebrandt lent her
considerable support to the project soon after. She is a director of
UNISA’s IDEAS institute. She has been the recipient of a number of
prestigious scientific awards including the Meiring Naude Medal, the
Bill Neale-May Gold Medal, the Distinguished Woman Scientist Award and
an AfricanUnion Scientific Award. She has been the author or co-author
of over one hundred and fifty peer-reviewed scientific publications
including three textbooks and an invited paper in Science. By building
chemical and thermal models of greenhouses as bio-reactors, we have been
able to develop fundamental insights into cause-and-effect relationships
in greenhouse design and operation. We found that greenhouse operation
is constrained by the necessity of supplying adequate CO2 for
photosynthesis. Since CO2 is highly dilute, this constraint demands a
very high air-flow through a greenhouse which in turn causes excessive
water evaporation and heat losses. Consequently, providing enriched CO2
can drastically reduce the heat and water requirements of a greenhouse.
In a paper currently in the final stages of review, we showed that using
membrane separation to partially enrich air as a feed can cut water
usage considerably. We also investigated the possibility of using power
station flue gas as a source of enriched CO2. In a recent paper, we
quantified the potential costs and benefits of diverting flue gases from
gas-fired power stations into greenhouses, finding that this approach
can achieve large-scale carbon capture without costly separation, while
massively boosting agricultural output and drastically reducing water
requirements. And so, we are here to field your questions as we advocate
for putting greenhouse gases into actual greenhouses. We’ll be back at
12 pm ET to answer your questions, Ask Us Anything! Edit: Diane is
awaiting a plane to Johannesburg, while Neil is out for a drink at
South-West London’s best bar, Dutch Courage, so there will be a bit of a
go-slow here until Neil is back home, around 2pm ET.