BIOFUEL AND WOOD AS ENERGY SOURCES
KNAW, Trippenhuis, Amsterdam — April 2015

Sustainable Energy – without the hot air


David MacKay FRS

Department of Engineering
University of Cambridge

Former Chief Scientific Advisor
Department of Energy and Climate Change
United Kingdom Government


   

One lane of cars

60 miles per hour
 
30 miles per gallon
1200 litres of biofuel per hectare per year
80 metres car-spacing

One lane of cars

60 miles per hour
30 miles per gallon
1200 litres of biofuel per hectare per year
80 metres car-spacing

= 8 kilometres wide

This book is free online


www.withouthotair.com

This book is free online


www.withouthotair.com

De Energievoorziening van Nederland — Delft Energy Initiative (2010)


www.tudelft.nl/onderzoek/thematische-samenwerking/delft-research-based-initiatives/energy/onderzoek/cijfers-over-energie/

The 2050 Calculator



2050-calculator-tool.decc.gov.uk

The Global Calculator - globalcalculator.org

(point size shows land area)

Photo provided by the University of Illinois

Plant power per unit area


* assumes genetic modification, fertilizer application, and irrigation
For sources, see D J C MacKay (2008) Sustainable Energy - without the hot air

Powers per unit area of British wind farms, v farm size


20 W/m2


Data and photo by Jonathan Kimmitt - 25 sq m of panels

Bavaria Solar Park: 5 W/m2
www.powerlight.com

3.8 W/m2
Photo by Robert Hargraves
Data from www.allearthrenewables.com

14 W/m2
www.stirlingenergy.com

Andasol, Spain

10 W/m2

RWE.com

PS10, Solucar

5 W/m2


Photo by afloresm
Ivanpah CA: 377 MW capacity
1079 GWh/y (123 MW)
  from 14.2 km2 of land
Power per unit area: 8.7 W/m2
Kagoshima: 70 MW capacity
expected load factor 12.8%.
1.04 km2 of land
Power per unit area: 8.6 W/m2
Solana AZ: 280 MW capacity
944 GWh/year (108 MW)
  from 12.6 km2 of land
Power per unit area: 8.6 W/m2

All renewables are diffuse

Wind 2.5 W/m2
Plants 0.5 W/m2
Solar PV panels 5–20 W/m2
Tidal pools 3 W/m2
Tidal stream 8 W/m2
Rain-water (highlands) 0.24 W/m2
Concentrating solar power (desert)      15–20 W/m2

   Fission: 1000 W/m2   

A consultation exercise in full swing




Demand-side options - Transport


Have small frontal area per person
Have small weight per person
Go slowly
Go steadily
Convert energy
    efficiently


We need a plan that adds up!



We need a plan that adds up —





... every month, every day, and every hour!
Electricity, gas, and transport demand; and fictional wind (assuming 33 GW of capacity), all on the same vertical scale.

End of Part 1

Comment:

many people are deluded about the scale of "renewables and energy efficiency" required to make a difference.

What about bioenergy and climate-change action?

UK Government Carbon Plan 2011

   

In the long term:
  • View bioenergy as a scarce resource;
  • use it for demands that are difficult to electrify:
    • freight, flight, shipping; industry
    • (not for making electricity, except in CCS power stations; not for heating buildings)

The size of future climate change depends on cumulative emissions


DECC/Met Office, adapted from IPCC 5th Assessment Report (2013)
Source: IPCC

Policies

  • Renewable transport fuel obligation
  • Renewable obligation (electricity)
  • Renewable heat incentive
  • International negotiations: prevention of deforestation


Vancouver to Immingham: 8888 nautical miles

"BEaC"

Roundwood and energy crops

   

Wastes and residues

Roundwood and energy crops


Using these assumptions, and assuming all harvested wood goes to power station
Area required for 30 M odt/y of pellets, delivering roughly 35 TWh/y:
about 40,000-50,000 km2 (two Wales)

Scenarios involving North American roundwood and energy crops

GHG intensity at 40 years

GHG intensity at 40 years

Wastes and residues

Scenarios involving North American woody residues

GHG intensity at 40 years



This is "Scenario 18" in the BEAC report

What to do? - some options

Extra slides on AR5, Bioenergy, and CCS

Reflections on the IPCC Fifth Assessment Report

AR5

"There are multiple mitigation pathways that are likely to limit warming to below 2°C relative to pre-industrial levels. These pathways would require substantial emissions reductions over the next few decades and near zero emissions of CO2 and other long-lived GHGs by the end of the century. Implementing such reductions poses substantial technological, economic, social, and institutional challenges, which increase with delays in additional mitigation and if key technologies are not available. Limiting warming to lower or higher levels involves similar challenges, but on different timescales. {3.4}"
AR5 synthesis report November 2014



... let's look at bioenergy and BECCS

How much bioenergy?

How much bioenergy?


450ppm: 275 EJ/year primary energy, and 75% going to BECCS
550ppm: 200 EJ/year, 60% going to BECCS
baseline: 140 EJ/year

275 EJ/year

= 23 kWh/d/person × 9 billion people

assuming 0.5 W/m2, requires 17 million km2
roughly 10% of world's land surface area

roughly 17 Gt per year of biomass
Is there any inconsistency?

Page 73 of SR:
Rural areas are expected to experience major impacts on water availability and supply, food security, infrastructure, and agricultural incomes, including shifts in the production areas of food and non-food crops around the world (high confidence). These impacts will disproportionately affect the welfare of the poor in rural areas, such as female-headed households and those with limited access to land, modern agricultural inputs, infrastructure, and education. {WGII 5.4, 9.3, 25.9, 26.8, 28.2, 28.4,Box 25-5}




64 GW of wind (20 GW average output)

Plant power per unit area


* assumes genetic modification, fertilizer application, and irrigation
For sources, see D J C MacKay (2008) Sustainable Energy - without the hot air

"Limited bioenergy"


"Limited Bioenergy":

"a maximum of 100 EJ/yr modern bioenergy supply globally (modern bioenergy used for heat, power, combinations, and industry was around 18 EJ/yr in 2008)."
(AR5-WG3)

So "limited" means 5.6-fold increase(!),
whereas 275-300 EJ/y is a 15-17-fold increase over 2008.

100 EJ/y / 9 billion people = 8.5 kWh/d per person

So UK 'share' would be
100 EJ/y × 75 million / (9 billion ) in GW = 26.4 GW
100 EJ/y × 75 million / (9 billion ) / (0.5 W/m2) in km2
= 52 814 km2
2.5 Waleses


100 EJ/y / 6e9 = 12.7 kWh per day per person
100 EJ/y / 7.125e9 = 10.7 kWh per day per person
projected population of UK: 75 million in 2100

100 EJ/y / 9 billion people
2.34 New Jerseys
2.54 Wales

using today's population
((100 (exajoules / year) × 64 million) / 7.125 billion) / (0.5 ((W / m) / m)) =
57000 km2 - nearly 3 Wales

How much bioenergy? In summary:




Vancouver to Immingham: 8888 nautical miles

Source: IPCC

How much carbon burial?



10-20 (or 40) Gt CO2 / year

(85 M barrels per day)

World Oil Production by Plazak.
Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons

Extra slides on BEAC

Energy Input Requirement - North Am roundwood and energy crops

Energy Input Requirement - North Am roundwood and energy crops

Energy Input Requirement - North Am roundwood and energy crops

Energy Input Requirement - North Am woody residues

Energy Input Requirement - North Am woody residues

Biomass Emissions and Counterfactual Model (speaking notes)

Bioenergy is expected to contribute significantly to the UK’s renewable target (for renewable sources to represent at least 15% of total energy consumption by 2020).
Bioenergy is also projected to help the UK meet carbon targets made under the Climate Change Act of 2008, where the UK must reduce its greenhouse gas emissions by at least 80% on 1990 levels, by 2050.
The UK Government therefore committed in its 2012 Bioenergy Strategy to support bioenergy that delivers genuine carbon reductions and helps to meet the UK’s decarbonisation targets.
The Bioenergy Strategy also identified risks and uncertainties associated with bioenergy, including whether it genuinely contributes to carbon reductions. The UK Government therefore also committed to continually updating our evidence base, and staying on top of the science.
One area that has (since 2012) been identified as requiring further work is the impact of bioenergy on forest carbon stocks. The Renewable Energy Directive sets out a methodology for assessing the carbon impacts of bioenergy, but does not include any emissions from changes in the carbon stock of forests.
To address both the need for further analysis and the uncertainty associated with carbon impacts, I and DECC's Science and Innovation team developed a model to investigate the overall carbon and energy impacts of different bioenergy scenarios for electricity generation. This is called the BEAC model, which stands for Biomass Emissions and Counterfactual Model.

The work shows that some bioenergy scenarios save considerable carbon emissions, whilst others can cause emissions greater than fossil fuels over time periods up to 100 years. Other studies show a similar range of carbon impacts.
For example, generating electricity from forest residues that would otherwise be burned as a waste has a very low carbon impact (near zero). However, if a forest is harvested more frequently than would otherwise happen in order to harvest additional wood for electricity generation, the electricity would likely have a very high carbon impact (greater than electricity from coal, when analysed over 100 years).
BEAC demonstrates that we must calculate and pay attention to changes in land carbon stocks to be confident that bioenergy policy genuinely contributes to our low carbon objectives. DECC will use the BEAC work to inform our bioenergy policies, and help ensure that only low carbon bioenergy is supported.

Conclusions

  • In 2020 it may be possible to meet the UK’s demand for solid biomass for electricity using biomass feedstocks from North America that result in electricity with a GHG intensity lower than 200 kg CO2e/MWh.
  • However, there are other bioenergy scenarios that could lead to high GHG impacts (e.g. greater than electricity from coal, when analysed over 40 or 100 years) but would be found to have GHG intensities less than 200 kg CO2e/MWh by the Renewable Energy Directive LCA methodology.
  • The energy input requirement of biomass electricity generated from North American wood used by the UK in 2020 is likely to be in the range 0.13 to 0.96 MWh energy carrier input per MWh delivered energy, significantly greater than other electricity generating technologies, such as coal, natural gas, nuclear and wind.

Scenarios involving woody residues (GHG intensity at 100 years)

Scenarios involving North American roundwood and energy crops (GHG intensity at 100 years)

This book is free online


www.withouthotair.com

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