have dramatically increased the efficiency of producing clean hydrogen fuel
from plant waste in a breakthrough that could one day lead to petrol stations
being replaced by a network of roadside “bioreactors” for refueling
cars. A study funded by Shell Oil has shown that it is possible to convert 100%
of the sugar stored in corn stover – the stalks, cobs and husks leftover in a
harvested maize field – into hydrogen gas with no overall increase in carbon
dioxide emissions to the atmosphere.
process was perfected by mixing raw biomass with a watery solution containing a
cocktail of ten enzymes that turned plant sugars xylose and glucose into
hydrogen and CO2, said Professor Percival Zhang of Virginia Tech in Blacksburg,
Virginia. Previously, it has only been possible to convert 30%-60% of the
sugars into hydrogen using either fermenting microbes or industrial catalysts.
However, the new technique converts 100% of the sugars into hydrogen.
pure hydrogen gas from crop waste and biomass is seen as one of the most
important goals of the green economy because of the need to produce clean
alternatives to petrol. However, existing methods are inefficient, costly and
are dogged by the problem of how to distribute the hydrogen once it is made. “All
the products produced by the process are gases so they can be separated and
collected easily from the biomass substrate. Over its lifecycle, the process is
carbon neutral and we have achieved a 17-fold increase in the rate of the
reaction which makes it economically viable,” Professor Zhang said. “…This means we have demonstrated the
most important step toward a hyd8rogen economy – producing dist8ributed and
affordable green hyd8rogen from local biomass res8ources,” Zhang said.
of the critical developments in the process is being able to directly use
“dirty” biomass as the fuel rather than relying on highly processed
sugars as the source of hydrogen. In addition to being more efficient, this
means it should also be possible to build large bioreactors the size of petrol
stations near to sources of biomass, so leading to a network of green
re-fuelling stations distributed around the country, Professor Zhang explained.
“The next problem is to work on how to scale it up. But if we receive
further funding I think in three to five years we should be able to build a
bioreactor that is something like a gas station which can produce 200 kilos of
hydrogen fuel a day. This would be enough to re-fuel about 40 or 50 cars,”
he told The Independent.
key step in the study was to identify the precise combination of enzymes that
would work together on the plant waste to convert all of its xylose and glucose
– which together account for 90 per cent of the sugars in plant waste – into
hydrogen and carbon dioxide, which can be collected separately. These 10
enzymes were initially made in microbial fermenters using genetically
engineered bacteria. The separated enzymes were then added to the solution of
plant waste where they continued to work for several weeks. However, the aim
eventually is for these enzymes to continue working for months or years without
being replaced, Professor Zhang said. (Source: TNN)