Transport is a big problem area, consuming around 30% of world
energy, nearly all via the use of fossil fuels. Whereas it’s relatively easy to
see how green energy sources can meet power needs and even heating needs,
mobility is a harder nut to crack, as we explore in this two part post.
In this first part we focus on road transport, which is responsible for around 15% of global
emissions and around three quarters of total transport emissions, the first
question to ask is – do we want to have private and commercial vehicles on roads
as at present? Buses, trams, trains, bikes and walking may be better for many
journeys- in environmental and also, compared to cars, in health terms: http://www.ukerc.ac.uk/network/network-news/guest-blog-buses-bicycles-and-building-for-health.html
But assuming we still need private and commercial road vehicles for at least
some purposes, the most direct and least disruptive way to reduce greenhouse
gas emissions is to switch to lower carbon fuels- biofuels and synfuels. However, even if the rate of use of biofuels
is matched by the rate of replanting, there are still net carbon debts and eco-impacts-
it takes energy to harvest and process the crops, CO2 remains in
the atmosphere while the new plants grow, biodiversity may be undermined and
there can be land-use conflicts with food growing. And with some low-yield
biofuel crops the energy gains are marginal. More productive advanced biofuel crops may
improve on that, but the fuel cycle is still not carbon free, and the
eco-impacts remain a big concern. Views differ, but it seems unlikely that we
could grow enough biofuels to replace significant amounts of petrol and diesel
use without having major eco-impacts.
Synthetic fuels of various kinds may be better, but so far the
costs are high. For example, it is possible to use electricity from wind or PV
solar systems to electrolyse water to make 100% green hydrogen gas, for use either
via combustion directly in car engines, or to run a fuel cell to make
electricity for an electric motor drive. Unfortunately, these multiple ‘Power
to Gas’ and ‘Gas to Power’ conversion steps each involve energy losses. If you
have cheap electricity to start with that may not matter too much (and if its
surplus wind or PV power, then it is in effect free), but even so, why not use
it direct in a battery electric car? The conversion loses are then very low.
Certainly electric vehicles seem to be winning against hydrogen
cars so far. Delivering electricity to car batteries is more straightforward
than delivering liquid hydrogen to an on-board cryogenic tank. However,
batteries are heavy and limit the car’s range. They are getting better, but in
time some of the other options may win out in some sectors. For example,
biofuels may have sourcing problems, but biogas, produced by anaerobic
digestion of farm and food wastes, is a relatively cheap and quite widely available
source and can be used in vehicles- although the volumes may not be very high. But
in addition, liquified synthetic methane (CH4) can made
from green hydrogen and CO2 captured from the air or from
power station exhausts. That could be good for trucks and vans. Some also look to synthetic methanol made from
methane, or even ammonia as a new carbon molecule-free fuel. But both are toxic…
For the moment most of the emphasis is on electric vehicles -
and on stimulating up take. They may
cost less to run than conventional cars, but the battery pack adds to the cost
and has to be replaced regularly. They also need charging! EV owners can charge them at home, which may
be fine for short commuting/shopping trips but for longer distance trips the UK
is trying to get more public charging points established around the country.
Ecotricity has already installed some at motorway services and there are some
provided for example by local councils at other sites, in all around 11,000.
The UK Department for Transport recently proposed plans to set common standards
for all public charge points. But its also supporting hydrogen refuelling
infrastructure.
Transport Secretary Chris Grayling said: ‘Our ambition is for nearly all new cars and vans to be zero emission
by 2040.’ And subsequently Environment
Secretary Michael Grove announced a plan to halt all new petrol and
diesel car sales by 2040. There is a way to go on that. But the Government has a £4m programme to help businesses to switch their large trucks and
vans to electric models through the Plug-In Van grant, as well as other grants
and incentives for EV purchase. As a result, the number of new registered
ultra-low emission vehicles (ULEVs) has risen by 250% in just two years, with
more than £600m pledged so far over this Parliament to boost the market. The
UK has the EUs second highest level of EV sales:
http://www.edie.net/news/6/Government-unveils-charging-plans-to-put-EVs-in-driving-seat/
However, it’s still pretty marginal, as is the uptake of
biofuels. The UK had agreed with an EU plan to increase the proportion of
biofuel included in fuel mixes sold but that has proved hard and caps have been
set by the EU in response to concerns about eco-impacts. At present liquid
biofuel contributes around 3% of the fuel used in UK road transport.
Sustainable sourcing has been an issue. Initially most biofuels were imported,
but, REA says that ‘UK biodiesel is now largely made from
waste feedstocks, in particular used cooking oil’, with no palm oil now being imported, and UK feedstocks for bioethanol
have risen, so overall 26% of biofuels are now UK sourced, up from 8% in 2008:
The situation in the USA is a bit different.
Biofuels, bioethanol especially, prospered initially, driven by subsidy schemes
aimed to help the beleaguered agricultural sector. Whether that helped much in
net energy and emission terms is debated. So too is the more recent boom in
electric vehicles (EVs). The US only gets around 15% of its electricity from
renewables (as opposed to 25% and growing in the UK), so most of the EVs aren’t
really very green. But the market for EVs is expanding. The Rocky Mountain
Institute says ‘During the last decade,
the number of plug-in vehicle models available for sale has grown to more than
20, just as battery costs have decreased by 70%, and the number of EV charging
stations across the U.S. has climbed to more than 16,000. And this growth
trajectory for EVs is likely to continue, especially with the Obama
administration’s announcement in July 2016 of actions to accelerate deployment
of EV charging infrastructure’.
However, the RMI notes that ‘load growth from new EVs can pose
challenges to the distribution system and to electricity customers—affecting
grid reliability and increasing electricity costs’. That’s also clear in
the UK- it could lead to a 20% extra peak power demand. But there are also some potential energy benefits.
For example, as RMI notes, ‘technologies
available today allow EVs to act as demand response resources and to assist
with the integration of renewable energy onto the grid by managing when and
where they charge’. Vehicle-to-grid (V2G) system need careful planning- no
one will like it if they find their car batteries drained when they want to go
somewhere or if the grid goes down if commuters all try to recharge their cars
when they get home from work! See the
RMI’s report, Driving Integration: Regulatory
responses to EV growth, for how these issue are
being faced in the USA: http://www.rmi.org/ev_integration
So what’s the bottom line? Although
public transport is by far the best environmentally, there are some green private
road vehicle options and they are likely to expand. So we might hope to slow
the rate of emissions in this sector. EVs
may come to the rescue, but it’s still pretty grim: road transport related emissions in the EU grew by 17%
between 1990 and 2014: http://www.eea.europa.eu/highlights/eu-greenhouse-gas-emissions-at
It’s even worse for ships and
planes. See the next post in this series.
