BP Educational Service
Science at Work
Biofuels and the future
Captured sunshine
Plants use sunlight for photosynthesis. This
process converts light energy into chemical energy.
All life depends on it, from simple algae to the
largest animals.
1.Animals do not photosynthesise. Why is
photosynthesis vital for all life on Earth?
The raw materials for photosynthesis are carbon
dioxide (CO2) and water.
6CO2 + 6H2O
C6H12O6 + 6O2
Light energy
The products are glucose and oxygen. Plants use
glucose for energy and growth.
A leaf from a photosynthesising plant
Around 200 million years ago, simple marine plants
thrived in warm seas. Together, they trapped
vast amounts of energy in their cells. Over time,
geological processes turned their remains into the
oil and gas we use today.
Stored energy from the Sun is also available in the
plants growing all around us now. As plants grow
and photosynthesise, they store energy from
sunlight in their stems and leaves. These are
known as biomass.
Biofuels are made from biomass. They use stored
chemical energy from plants. When they are
burned, the chemical energy is released.
‘There is no one magic
number which describes
the emissions reductions
for all biofuels – these all
vary enormously.’
Oil and gas reserves are limited, and world demand
for transportation fuels is growing. Scientists are
looking for creative new solutions, and one idea
is to use biomass. The energy in biomass can be
converted into liquid biofuels.
Business technology
manager, BP Biofuels
2.Why does the increasing demand for fuels
make biofuels important?
1
Why biofuels matter
Sugar cane - an efficient biofuel feedstock
3.How does burning fossil fuels increase the
amount of CO2 in the atmosphere today?
Greenhouse gases are essential for life. They trap
some of the Sun’s heat energy in the atmosphere.
This warms the Earth and allows the life we
see today to exist.
Biofuels are made from biomass on the Earth’s
surface. This biomass captures CO2 as it grows,
and then CO2 is released again when the fuel
is burned.
One greenhouse gas is carbon dioxide. In recent
decades, the amount of CO2 in the atmosphere
has increased. This appears to contribute to
global warming, the rise in average temperatures
around the world.
So it seems as though burning biofuels would not
affect the total amount of CO2 in the atmosphere.
In practice, some energy from other sources is used
in the growing and processing of the biofuel crops.
Biomass captures CO2 from the atmosphere as it
grows. Over many millions of years the biomass is
compressed in the Earth to form crude oil, coal or
natural gas, which we call fossil fuels.
4.Why would biofuels not be a good
solution if their production emitted a lot
of carbon dioxide?
When these fossil fuels are burned, CO2 that
has been trapped for millions of years is returned
to the atmosphere. In effect, burning fossil fuels
adds ‘new’ carbon to the total amount in
the atmosphere.
Biofuels can help reduce CO2 emissions if they are
carefully managed. Some biofuels are better than
others at reducing emissions. BP scientists believe
that selecting better biofuels and continuing to
develop new technologies will mean biofuels can
save up to 90% or more of the emissions produced
by conventional fuels.
2
What are biofuels made of?
Today’s biofuels can be made from many
familiar crops:
– Starch in corn and wheat can be converted into
sugar and then fermented to make bioethanol
– Sugar can be extracted from sugarcane and
fermented to make bioethanol
– Oils in rapeseed, soy and palm can be
processed to make biodiesel
Governments around the world are interested in
biofuels. Many have set targets to produce and
use more. If developed carefully, biofuels have
the potential to increase energy security, reduce
greenhouse gas emissions and support agriculture.
Concern about the sustainability of biofuel crop
cultivation, however, has led to debate.
Growing these crops for biofuel production can
be good for local farmers, but it may affect food
supplies. Because fuel is so important, farmers may
get more money by selling their crops for biofuel.
This could affect the price people must pay for these
crops as food. It may encourage farmers to cut
down forested areas to grow these crops.
Sugarcane plants
Scientists are investigating ways to minimise
this pressure by:
– increasing crop yields
– using land that is not used for food
5.How could growing a biofuel crop be good
for a community?
– developing non-food raw materials for biofuels
– creating new biofuel technology to process
those parts of plants that are not normally used
(e.g. leaves and stalks).
6.What might be the disadvantages of using
a food crop as biofuel?
It’s important that biofuels use feedstocks that
minimise any pressure on food supplies.
Developing new technology is a challenge:
a creative new idea is a good start, but there are
often many factors to think about before the idea
can become a really useful new product.
Biofuels are no exception. There are many things
to consider when deciding whether it is a good
idea to use a crop for biofuel production or not.
3
Making ethanol from plants
Ethanol from sugar cane
Sugar cane is a fast-growing grass that grows in hot
climates. It is very efficient at converting the sun’s
energy into biomass. In Brazil, ethanol from sugar
cane has been used as fuel in cars for over 30 years.
The sugarcane is shredded, mixed with water and
crushed. The solid waste parts, known as bagasse,
are removed.
– The remaining sugar solution is fermented
using yeast
– The fermented ethanol is distilled
– Any remaining water is removed.
Bagasse can be burned to provide the heat needed
to distil the fermented ethanol. But bagasse can
also be used to make ethanol, using a process like
the one below. This allows the whole of the sugar
cane plant to be used.
Ethanol from energy grasses
Many of today’s biofuels use the energy stored
in the starches, sugars or oils that biofuel crops
contain. But most of the Sun’s energy is converted
into chemical energy in other parts of the plant,
such as stems and leaves. These contain cellulose,
a long-chain molecule that is made up of sugar
molecules. But these cannot be fermented into
ethanol in the usual way.
Ethanol made from sugar cane can deliver
greenhouse gas reductions of up to 90%
compared to conventional fuels. It can also be
used as a feedstock for the next generation of
advanced biofuels, such as biobutanol and diesel.
7. Why does burning bagasse to distil the
ethanol help to reduce the greenhouse gas
contribution of sugar cane ethanol?
Miscanthus
Miscanthus is a tall grass with long stems and
leaves. It:
– Enjoys a cool climate
– Is easy to grow, and grows very fast
– Is perennial (will re-grow every year
without re-planting)
– Has long roots, which store carbon in the soil
– Can yield 3 – 4 times more biomass per
hectare than other crops.
New technologies convert the sugars in cellulose
into a different form. This can then be processed into
ethanol. These processes allow biofuels to be made
from the cellulose in Miscanthus or sugar cane.
8. Why is each point above a good reason to
use Miscanthus as a biofuel crop?
4
From sugar to diesel
Ethanol from biomass offers an alternative to
conventional petrol. But demand for diesel to
fuel vehicles also continues to grow, particularly
in Europe.
The challenge today is to enable cost effective
production at a commercial scale. BP and
its partners are working to identify the most
suitable micro-organisms and the most efficient
manufacturing method.
Today, biodiesel is produced from vegetable oils
like palm oil, soy bean oil and rapeseed oil. These
oils are increasingly associated with concerns
about sustainability.
Biodiesel from plant sugars will be an important new
product alongside ethanol-based gasoline (petrol).
Together, these will allow BP to meet the needs of
vehicles currently running on both types of fuel.
BP is investing in a new process that allows
biodiesel to be fermented from plant biomass.
This uses micro-organisms similar to the yeasts
that convert sugar into ethanol. But instead, these
micro-organisms convert the sugars into oils.
These oils can then be extracted and upgraded
into diesel.
9. The process that BP is choosing to pursue
can create more oils from the sugars that are
fermented. How does this help to minimise the
greenhouse gas emissions associated with this
form of biodiesel?
The sugars themselves can come from many
sources, including sugar cane or energy grasses
like Miscanthus. Using these feedstocks could
reduce greenhouse gas emissions by up to 8090% when compared to conventional diesel.
They provide a more sustainable choice than
using vegetable oils.
‘There are many
challenges to be met
along the way. Technology
will be the enabler for
meeting these challenges.’
Head of BP Biofuels
5
Using biofuels
Most cars on the road at the moment cannot use
‘pure’ biofuels. Instead, current biofuels are usually
blended with conventional petrol or diesel.
Ethanol can make up to 10% of the volume of
these blended fuels. The rest of the blend is fossil
fuels. This follows current fuels standards and
regulations, and avoids damage to car engines, but
it means that greenhouse gas reductions are less
than they could be.
10. Why does blending fuels reduce the
potential greenhouse gas savings of biofuels?
BP is working with other organisations to develop
advanced biofuels that:
– Can be blended in higher concentrations with conventional petrol
Wheat – one possible biofuel crop
– Provide more energy per litre than existing
biofuels
– Can be used without the need for engine
modifications.
These advanced biofuels have the potential to
reduce greenhouse gas emissions by more than
some existing biofuels.
BP is working with its partner DuPont to develop
biobutanol. This is a biofuel more like conventional
fuels, so up to 16% biobutanol can be added to
fuel blends. Biobutanol also has a superior energy
content to ethanol.
Together, these properties allow biobutanol blends
to offer twice the reduction in greenhouse gas
emissions compared to ethanol blends.
11. Why will biobutanol fuel blends allow
greater greenhouse gas savings than some
other biofuels?
6
Glossary
Biofuel – a fuel made from plants, which makes
use of the captured energy from the Sun that is
stored in plant material.
Biomass – the material in living (or recently living)
organisms, such as the plant matter that is used
for biofuels.
Ethanol – an alcohol with the formula C2H5OH.
Fermentation – the process by which singlecelled micro-organisms produce energy from
carbohydrates, without the use of oxygen.
Fossil fuel – a fuel made from plants that have
been compressed under the earth for many
millions of years, e.g. coal, oil or natural gas.
Greenhouse gas – a gas that contributes to the
greenhouse effect (the warming that occurs
when heat from the Sun is trapped in the Earth’s
lower atmosphere); carbon dioxide and methane
are two examples.
Global warming – the rise in average
temperatures that is the result of increased
greenhouse gas concentrations in the
atmosphere.
Photosynthesis – the process by which plants
convert light energy into chemical energy; carbon
dioxide and water combine to produce oxygen
and glucose.
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