Carbon-neutral 'biofuel' from lakes
Lakes could be suitable for the extraction of methane for energy
production

Date:
March 31, 2021
Source:
University of Basel
Summary:
Lakes store huge amounts of methane. In a new study, environmental
scientists offer suggestions for how it can be extracted and used
as an energy source in the form of methanol.



FULL STORY ========================================================================== Lakes store huge amounts of methane. In a new study, environmental
scientists at the University of Basel offer suggestions for how it can
be extracted and used as an energy source in the form of methanol.


========================================================================== Discussion about the current climate crisis usually focuses on carbon
dioxide (CO2). The greenhouse gas methane is less well known, but although
it is much rarer in the atmosphere, its global warming potential is 80
to 100 times greater per unit.

More than half the methane caused by human activities comes from oil
production and agricultural fertilizers. But the gas is also created by
the natural decomposition of biomass by microbes, for example in lakes. In their most recent publication, researchers at the University of Basel
in Switzerland outline the potential and theoretical possibilities for
using methane from lakes and other freshwater bodies for sustainable
energy production.

Methane from lakes and water reservoirs makes up about 20% of global
natural methane missions. "That would theoretically be enough to meet
the world's energy needs," says Maciej Bartosiewicz, a postdoc in the Department of Environmental Sciences of the University of Basel. Lakes continuously absorb CO2 from the atmosphere through the growth of phytoplankton. Microbes convert the carbon, fixed by photosynthesis,
into methane when they process biomass.

That way, carbon bound in the methane remains within the natural cycle
during combustion. Fossil fuels could be partially replaced by "natural" renewable methane. Methane gas is already burned in gas-fired power
plants for electricity production and used as a fuel in the form of
liquid methanol.

Lakes as huge energy stores The idea described in the article isn't
completely new: since 2016, methane in Lake Kivu between Rwanda
and the Democratic Republic of Congo has been extracted from a
depth of 260 meters, cleaned and used for energy supply directly via generators. "Methane occurs in high concentrations in large quantities on
the lake bed there," explains Bartosiewicz. "The methane concentration
is about 100 times higher than in ordinary lakes." Low concentrations
made extracting methane from conventional lakes seem too technically
difficult until a few years ago. But new microporous membranes made of polymeric materials now allow the gas to be separated from the water
much more efficiently.

The researchers have made the first concrete proposals in this
regard: using a hydrophobic gas-liquid membrane contactor, a
methane-containing gas mixture can be separated from water and the methane concentrated. Zeolite minerals are particularly suitable for enrichment,
since hydrophobic crystalline substances can adsorb and release gases.

Potential positive effects on ecosystems "With our idea, we wanted
to start a broad discussion about the potential, feasibility and
risks of a technology like this," says Bartosiewicz. "Until now,
no studies have addressed the effects of methane removal on lake
ecosystem functioning, but no immediate negative effects can be
foreseen with our current understanding." However, removing excess
carbon could even help curb excessive phytoplankton bloom formation
and reduce natural greenhouse gas emissions from lakes. More work is
needed before any practical implementation of this initial theoretical
idea, says Bartosiewicz. But he's convinced: "This concept could
one day make an important contribution to reaching our climate goals." ========================================================================== Story Source: Materials provided by University_of_Basel. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Maciej Bartosiewicz, Przemyslaw Rzepka, Moritz F. Lehmann. Tapping
Freshwaters for Methane and Energy. Environmental Science &
Technology, 2021; DOI: 10.1021/acs.est.0c06210 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/03/210331103612.htm

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