Transcript People, Wood, and Homes in the 21st Century

Materials and the Environment
(Most recent update January 7, 2006)
• Solving Environmental Problems
• General Global Trends
– Population
– Economy
• Raw Material Consumption Trends
– Wood
– Other Materials
• Options to Wood Use
Solving Complex Problems Requires
a Combination of:
• Rational thinking
• The use of realistic assumptions
• Global or systematic analysis
Environmental Problems
•
•
•
•
•
•
•
Species loss
Global warming
Acid rain
Ozone depletion
Population growth
Garbage/litter
Desertification
•
•
•
•
•
Tropical deforestation
Urban sprawl
Aquifer depletion
Topsoil erosion
Pollution of coastal
waters
• Wetlands loss
Population
World Population 1850-1950
20
50
20
30
20
10
19
90
19
70
19
50
19
30
19
10
18
90
18
70
18
50
10
9
8
7
6
Billions 5
4
3
2
1
0
Year
Source: U.S. Census Bureau, International Programs Center, 2002
World Population 1850-1950
20
50
20
30
20
10
19
90
19
70
19
50
19
30
19
10
18
90
18
70
18
50
10
9
8
7
6
Billions 5
4
3
2
1
0
Year
Source: U.S. Census Bureau, International Programs Center, 2002
World Population 1850-2005
Year
Source: U.S. Census Bureau, International Programs Center, 2006.
2010
2000
1990
1980
1970
1960
1950
1940
1930
1920
1910
1900
1890
1880
1870
1860
1850
8
7
6
5
Billions 4
3
2
1
0
World Population 1850-2005
Year
Source: U.S. Census Bureau, International Programs Center, 2006.
2010
2000
1990
1980
1970
1960
1950
1940
1930
1920
1910
1900
1890
1880
1870
1860
1850
8
7
6
5
Billions 4
3
2
1
0
World Population 1850-2050
(Medium Projection of Growth Assumed After 2000)
20
50
20
30
20
10
19
90
19
70
19
50
19
30
19
10
18
90
18
70
18
50
10
9
8
7
6
Billions 5
4
3
2
1
0
Year
Source: U.S. Census Bureau, International Programs Center, 2006.
Growth in Global Population
All of Human History
Number of years to add each billion (year)
All of recorded history
First Billion
Second
Third
123 (1930)
33 (1960)
Fourth
15 (1975)
Fifth
12 (1987)
Sixth
12 (1999)
Seventh
13 (2012)
Eighth
16 (2028)
Ninth
(1800)
26 (2054)
Sources: First and second billion: Population Reference Bureau. Third through ninth billion:
United Nations, World Population in 2300 (medium scenario), 2003.
Annual Increase in World Population,
1951-2005
Millions
100
90
80
70
60
50
40
30
20
10
0
1951
1956
1961
1966
1971
1976
1981
1986
1991
1996
2001
Source: United Nations, World Population Prospects: The 2002 Revision, 2003. Data for
1990 through 2005 from U.S. Census Bureau, International Division.
World Birth and Death Rates,
2003
1936-
Rates of birth, death, and natural increase per 1,000 population
40
35
30
25
Natural Increase
20
15
10
5
0
1936- 1946- 1955- 1960- 1965- 1970- 1975- 1980- 1985- 1990- 1995- 20001938 1948 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
Birth rate
Death rate
Source: United Nations, World Population Prospects: The 2002 Revision (medium scenario), 2003.
Rate of Population Increase - 2006
Time Unit
Year
Population Increase
74,281,173
Month
6,190,098
Week
1,428,484
Day
Hour
Minute
Second
205,510
8,480
141
2.4
Source: U.S. Census Bureau, International Division, 2006.
Average Annual Rate of Population Growth for
the World, 1950 – 2020 – Continuing Decline
Since 1970
2.5
Percent
2
1.5
1
0.5
0
50
9
1
60
9
1
70
9
1
80
9
1
90
9
1
00
0
2
10
0
2
Source: U.S. Census Bureau, International Division, 2004.
20
0
2
Medium Projections of Population
Growth
(billions)
World
2000
2050
2100
6.1
9.2
11.1
Source: U.S. Census Bureau, International Division, 2006.
The world population will increase 60
to 90 percent within the lifetime of a
child born today
Growth of U.S. Population, 1776- 2005
350
300
250
200
150
100
50
0
80
7
1
00
8
1
20
8
1
40
8
1
60
8
1
80
8
1
00
9
1
20
9
1
40
9
1
Source: U.S. Census Bureau, 2006.
60
9
1
80
9
1
00
0
2
Growth of U.S. Population, 17762100
600
500
400
300
200
Projection
100
History
17
80
18
00
18
20
18
40
18
60
18
80
19
00
19
20
19
40
19
60
19
80
20
00
20
20
20
40
20
60
20
80
21
00
0
Medium Projections of Population
Growth
(world population in billions,
U.S. population in millions)
2000
2050
2100
World
6.1
9.2
11.1
United States
282
420
571
Source: U.S. Census Bureau, International Division, 2006.
Growth of Minnesota Population,
1950- 2005
7
6
5
4
3
2
1
0
1950
1975
2000
202
Growth of Minnesota Population,
1850- 2100
10000000
9000000
8000000
7000000
6000000
5000000
4000000
3000000
2000000
1000000
0
Projection
Projection
History
50 870 890 910 930 950 970 990 010 030 050 070 090
8
1
1
1
1
1
1
1
1
2
2
2
2
2
Source: U.S. Census Bureau, 2006.
Medium Projections of Population
Growth
(world population in billions,
U.S. and Minnesota populations in millions)
2000
2050
2100
World
6.1
9.2
11.1
United States
282
420
571
Minnesota
4.9
7.1
9.4
Source: U.S. Census Bureau, International Division, 2006.
World and U.S. populations will grow
substantially within the lifetime of a
child born today
No less significant, the world will be
faced in the 21st century with the
challenge of providing food, fuel,
shelter, and clothing for a much larger
population.
Economy
Gross Domestic Product:
The value of all goods and services
produced within the borders of a
nation
Gross World Product:
The sum of all Gross Domestic
Product values expressed in a
common currency.
Gross World Product, 1970-2004
Trillions of 1990 U.S. dollars
35
30
25
20
15
10
5
0
An increase of 174 percent.
World population increased about 72 percent
over the same period.
0 73 76 79 82 85 88 91 94 97 00 03
7
19 19 19 19 19 19 19 19 19 19 20 20
Source: United Nations Statistics Division, 2005.
Annual Growth in Gross Domestic Product for
Nations Classified by Average Incomes,
1980-1990 and 1990-1998
Income Category
Low income
Low income excl. China and India
Middle income
Lower middle income
Upper middle income
Low and middle income
East Asia and Pacific
Europe and Central Asia
Latin America and Caribbean
Middle East and N. Africa
South Asia
Sub-Saharan Africa
High income
World
1981-1990
6.6
4.1
2.6
-2.7
3.5
8.0
-1.6
2.0
5.7
1.8
3.1
3.2
Source: World Bank, 2001
1990-1998
7.3
3.6
1.9
-1.3
3.9
3.3
8.1
-4.3
3.7
3.0
5.7
2.2
2.1
2.4
China’s Gross Domestic Product
Billions of 1987 U.S. Dollars
(Exchange Rate Valuation)
2500
2000
1500
1000
500
0
1980 1985 1990 1995 2000 2005 2010 2015
Source: U.S. Department of Energy, Energy Information Administration, 2002.
It is a virtual
certainty that
consumption of raw
materials globally
will increase
substantially in the
future.
Considering the combined effect of
population growth and economic
growth within developing nations,
demand for new housing units globally
over the next 50 years is likely to
exceed one billion.
How in the world is
society going to be
able to pull this off
and wind up with an
environment that
most of us would
agree is acceptable for our
for our children and grand-children?
Raw Material
Consumption
Trends
U.S. Growth in Basic Raw
Materials Consumption, 1970-2004
(Population growth during this period: 1.43x)
Steel Cement
1.00x
1.80x
Aluminum
Plastics
Wood
Products
1.85x
5.28x
1.38x
Source: Data for wood from USFS (2005); for cement, steel, and aluminum from the U.S.
Geological Survey (2006); and for plastics from the National Commission on Materials
Policy (1975) and the APC Plastics Industry Council (2006).
World Growth in Basic Raw
Materials Consumption, 1970-2004
(Population growth during this period: 1.72x)
Steel
Cement
1.60x
3.50x
Aluminum
3.00x
Plastics
Wood
6.83x
1. 27x
Source: Data for wood from FAO (2006); for cement, steel, and aluminum
from the U.S. Geological Survey (2006); and for plastics from the
Association of Plastics Manufacturers in Europe (2002) and from Plastics
Today magazine (2005).
Wood
Wood is a principal raw material in
the world today.
Annual World Consumption of Various Raw
Materials, 2004
Roundwood
Industrial roundwood
Cement
Steel
Plastics
Aluminum
Billion
Metric tons
1.679
0.794
2.000
0.949
0.205
0.029
Billion m3
3.4
1.6
1.9
0.11
0.18
0.01
Source: Data for wood from FAO (2006); for cement, aluminum, and steel from the U.S.
Geological Survey (2006);and for plastics from the Association of Plastics Manufacturers in
Europe (2002) and from Plastics Today magazine (2005).
Annual U.S. Consumption of Various Raw
Materials, 2004
Million
Metric tons
Roundwood
301
Industrial roundwood
277
Forest products (wd only) 180
Cement
121
Steel
125
Plastics
39.1
Aluminum
6.3
Million m3
556
512
296
110
158
34.5
2.2
Source: Data for wood from USFS (2005); for cement, steel, and aluminum from the
U.S. Geological Survey (2006); and for plastics from the National Commission on
Materials Policy (1975) and the APC Plastics Industry Council (2006).
U.S. Demand For Wood and Wood
Products, 1800 - 2002
(Million Cubic Feet, Roundwood Equivalent)
25
20
Plywd/Ven
Pulp
Lumber
Other Ind.
Fuelwood
15
10
5
1995
1982
1969
1956
1943
1930
1917
1904
1891
1878
1865
1852
1839
1826
1813
1800
0
Source: Howard, J. 2004. U.S.D.A.- Forest Service, USFPL.
Global Wood Harvest, 1950 to 2004,
with Projection to 2010
4000
3500
Million m3
3000
2500
2000
1500
1000
500
0
1950
1960
1970
1980
1990
2004
2010
Source: FAO (2005)
Million m3
Global Wood Harvest, 1950 to 2004
4000
3500
3000
2500
2000
1500
1000
500
0
Indust. Wood
Fuelwood
1950
1960
1970
1980
1990
2004
Source: FAO (2005)
Global Wood Harvest and Population,
1950 to 2004
4000
3500
3000
2500
8
2000
1500
1000
500
0
4
6
2
1950
1960
1970
1980
1990
2004
0
Source: FAO (2005); U.S. Census Bureau, Int’l Division (2005)
Population (Billions)
Harvest (Million m3)
Harvest
Population
The Amount of
Biosphere Per Person
Grows Smaller
As The Population Grows . . .
The Same Is True of Forests
Forests Then and Now - World
• In 1800
– World population was 1 billion
– There were about 11 acres of forests for
each person in the world
Forests Then and Now - World
• In 1800
– World population was 1 billion
– There were about 11 acres (4.5 ha.) of
forests for each person in the world
• Today
– World population is over 6 billion
– There are about 1.4 acres (0.6 ha.) of forest
for each person in the world
Forests Then, Now, and Future World
By the end of the next century
– World population is expected to reach 10 to 11 billion
– Even with zero loss of forests over the next 100 years,
the amount of forest land for each person in the world
will shrink to 0.7 to 0.8 acres (or about 0.3 ha.)
Forests Then and Now – U.S.
Forest Area
(million ac.)
Forest
Area/
Capita
(acres)
348
Year
Population
1785
3,000,000
1,044
1850
23,300,000
926
1910
77,000,000
730
9.5
2000
281,000,000
747
2.7
40
Forests Then, Now, and Future – U.S.
Forest
Area/Capita
(acres)
348
Year
Population
1785
3,000,000
Forest Area
(million ac.)
1,044
1850
23,300,000
926
1910
77,000,000
730
9.5
2000
281,000,000
747
2.7
2100
571,000,000
747
1.3
40
Forests Then, Now, and Future – Minnesota
Forest
Area/Capita
(acres)
5.7
Year
Population
1950
2.99 million
Forest Area
(million ac.)
17.4
2000
4.91 million
14.8
3.1
2100
8.90 million
14.8
1.6
Sharp reductions in forest land/ capita
virtually ensure escalating conflict
over forest use, and raise the question
of where needed wood supplies will
come from in the future.
U.S. Trends in Raw
Material Procurement
The U.S. is a net importer of most
categories of raw materials used to
support our economy and lifestyle.
The U.S. is a net importer of most
categories of raw materials used to
support our economy and lifestyle.
•
•
•
•
Most metals
Portland and masonry cement
Petroleum (the basis for plastics)
Wood and wood products
Net U.S. Imports of Selected Materials as a Percent
of Apparent Consumption - 2004, and by Major
Foreign Sources
Material
% Imported
Columbium
100
Mica (natural)
100
Manganese
100
Graphite
100
Strontium
100
Bauxite/Alumina
100
Fluorspar
100
Yttrium
100
Thallium
100
Rubidium
100
Principal Foreign Sources
Brazil, Canada, Estonia, Germany
India, Belgium, China, Germany
S. Africa, Gabon, Australia, France
China, Mexico, Canada, Brazil
Mexico, Germany
Australia, Jamaica, Guinea, Suriname
China, S. Africa, Mexico
China, Japan, Austria, Netherlands
Belgium, France, Russia, UK
Canada
Net U.S. Imports of Selected Materials as a Percent
of Apparent Consumption - 2004, and by Major
Foreign Sources
Material
% Imported
Asbestos
100
Quartz (crystal)
100
Arsenic (trioxide)
100
Indium
100
Rare earth metals
100
Rubidium
100
Vanadium
100
Gemstones
99
Platinum Group
91
Bismuth
90
Principal Foreign Sources
Canada
Brazil, Germany, Madagascar
China, Chile, Morocco, Mexico
China, Canada, Japan, France
China, France, Japan, Estonia
Canada
Czech Rep., S. Africa, Canada, China
Israel, India, Belgium
S. Africa, UK, Germany, Canada
Belgium, Mexico, China, UK
Net U.S. Imports of Selected Materials as a Percent
of Apparent Consumption - 2004, and by Major
Foreign Sources
Material
% Imported
Tin
88
Stone (dimension)
85
Diamond (indust)
85
Titanium (sponge)
85
Palladium
81
Tantalum
80
Barium (Barite)
79
Rhenium
79
Cobalt
76
Iodine
74
Principal Foreign Sources
Peru, China, Bolivia, Brazil
Italy, Canada, India, Spain
Ireland, Switzerland, UK, Russia
Kazakhstan, Japan, Russia
Russia, S. Africa, UK, Belgium
Australia, Kazakhstan, Canada, China
China, India
Chile, Kazakhstan, Mexico
Finland, Norway, Russia, Canada
Chile, Japan, Russia
Net U.S. Imports of Selected Materials as a Percent
of Apparent Consumption - 2004, and by Major
Foreign Sources
Material
Tungsten
Chromium
% Imported
Principal Foreign Sources
73
China, Canada
72
S. Africa, Kazakhstan, Zimbabwe,
Russia
Potash
70
Canada, Belarus, Russia, Germany
Magnesium Metal
68
Canada, China, Russia, Israel
Titanium concentrates 65
S. Africa, Australia, Canada, Ukraine
Petroleum
58
Canada, Saudi Arabia, Mexico,
Venezuela, Nigeria
Silicon
56
S. Africa, Norway, Brazil, Russia
Zinc
56
Canada, Mexico, Peru
Net U.S. Imports of Selected Materials as a Percent
of Apparent Consumption - 2004, and by Major
Foreign Sources
Material
% Imported
Beryllium
55
Silver
54
Lithium
>50
Nickel
49
Magnesium Cpds
48
Copper
43
Aluminum
41
Diamond (dust, grit) 40
Nitrogen (fixed)
38
Lumber (softwood)
37
Principal Foreign Sources
Kazakhstan, Japan, Brazil, Spain
Mexico, Canada, UK, Peru
Chile, Argentina
Canada, Russia, Norway, Australia
China, Australia, Canada, Austria
Canada, Chile, Peru, Mexico
Canada, Russia, Venezuela, Mexico
Ireland, China, Ukraine
Trinidad and Tobago, Canada, Russia
Canada, EU, Chile, N. Zealand, Mex.
Net U.S. Imports of Selected Materials as a Percent
of Apparent Consumption - 2004, and by Major
Foreign Sources
Material
% Imported
Mica
35
Garnet (industrial)
34
Pumice
26
Perlite
23
Gypsum
26
Salt
20
Cement (Port/msry) 23
Sulfur
20
Iron and steel
18
Principal Foreign Sources
Canada, India, China, Finland
Australia, India, China
Greece, Italy, Turkey
Greece
Canada, Mexico, Spain
Canada, Chile, Mexico, The Bahamas
Canada, Thailand, China, Venezuela
Canada, Mexico, Venezuela
EEC, Canada, Mexico, S. Korea
Net U.S. Imports of Selected Materials as a Percent
of Apparent Consumption - 2004, and by Major
Foreign Sources
Material
% Imported
Principal Foreign Sources
Wood/Wd. Prod.
12
Canada, China, Indonesia, Finland,
N. Zealand, Chile, Brazil
Iron ore
8
Canada, Brazil, Australia, Chile
Phosphate rock
6
Morocco
Iron and steel slag
5
Canada, France, Italy, Japan
Talc
1
China, Canada, France, Japan
Also significant import dependency for Arsenic, Cesium, Gallium, Germanium, Leather, Natural
Rubber, Selenium, Wool, Zirconium.
Source: US Geological Survey, 2004.
The United States is also a net
importer of durable and non-durable
goods of all kinds.
The United States has been a net
importer of wood and wood products
for over 35 years.
Is Minnesota a net importer or net
exporter of wood and wood products?
Growing Stock Consumption
Removals
Non-growing Stock Consumption
2897
70
117
613
274
761
62
Million Cubic Feet
370
88
226
753
174
66
34 178
327
332
490
56 297
207
Source: Shifley and Sullivan, U.S.F.S. - North Central
Experiment Station (2002).
551
Growth
1106
144
340
2335
65
117
267
22
42
375
Timber Growth, Removals, and Consumption by State
All NC
Timber Growth, Removals, and Consumption by Region
6
Pacific
Northwest
4
North Central
2
25
Northeast
All U.S.
6
4
Intermountain
4
6
2
2
4
0
0
2
2
2
0
Pacific
Southwest
20
2
2
4
2
South Central
0
6
6
4
2
6
4
2
Alaska
Southeast
57
Billion Cubic Feet
0
6
6
15
10
4
2
5
2
0
0
2
2
0
0
2
Growth
Growing Stock Consumption
Removals
Non-growing Stock Consumption
Source: Shifley and Sullivan, U.S.F.S. - North Central Experiment Station (2002).
Minnesota is a net importer of wood.
The 2002 harvest from Minnesota’s
forests was 3.7 million cords - about
3
59 ft. of wood per capita. Annual
U.S. consumption of wood is about
67 ft.3 per capita, giving an apparent
net import figure of 13.5%.
Forest Area Needed to Supply Wood
Needs of Various Metropolitan Areas
Minneapolis//St. Paul
Des Moines
Chicago
Based on:
1) currently available estimates of
net annual growing stock
growth per county
2) 2000 population census
3) 73 ft3 per capita consumption
4) no consumption in outlying
counties
St. Louis
0
200
400 Miles
Figure 15
Environmental Impacts of Materials
Production
Life Cycle Inventory (LCI)
Examination of all measurable:
•Raw material inputs
•Products and by-products
•Emissions
•Effluents
•Wastes
Life Cycle Inventory (LCI)
Typically involves all stages in production, use,
and disposal, including:
•Extraction
•Transportation
•Primary processing
•Conversion to semi-finished products
•Incorporation into finished products
•Maintenance
•Disposal/reuse
Life Cycle Analysis (LCA)
Examines costs associated with specific
environmental burdens:
•Cleanup costs
•Health impacts
•Landscape impacts
•Environmental impacts
Consider for a moment the
environmental impacts of decisions
regarding the construction of a
residential home.
Relative Energy Consumption to
Produce a Ton of:
Material
Energy
Aluminum
70
Steel
17
Brick
3.1
Concrete Blocks
3.0
Dry Lumber
1.0
Source: CORRIM I, National Research Council, 1976.
Comparative Energy Consumed in
Manufacturing Wood vs. Steel-Framed Interior
Wall (GJ)
Wood Stud Wall
Steel Stud Wall
Extraction
0.7
1.2
Manufacturing
2.1
9.7
Construction
0.6
0.6
Total
3.4
11.5
Source: Athena Sustainable Materials Institute, 1993.
Comparative Energy Consumed in
Manufacturing Wood vs. Steel-Framed Interior
Wall (GJ)
Wood Stud Wall
Steel Stud Wall
Extraction
0.7
1.2
Manufacturing
2.1
9.7
Construction
0.6
0.6
Total
3.4
11.5
3.4x
Source: Athena Sustainable Materials Institute, 1993.
What about an exterior wall?
What if the steel has 50% recycled
content?
Net Carbon Emissions in Producing a Ton of:
Material
Framing lumber
Concrete
Concrete block
Brick
Glass
Steel
Aluminum
Plastic
Net Carbon Emissions
(kg C/metric ton)
-460
45
49
148
630
1,090
2,400
2,810
Source: Honey and Buchanan, Department of Civil Engineering,
University of Canterbury, Christchurch, NZ, 1992.
Carbon Dioxide Emissions of Various
Components in a Typical House
Net Carbon Emission (kg C)
2000
1500
1000
Timber
Steel
Concrete Slab
500
0
-500
-1000
-1500
House Frame
Floor
Wall
Source: Honey and Buchanan, Department of Civil Engineering, University of Canterbury,
Christchurch, NZ, 1992.
Carbon Dioxide Emissions of Various
Components in a Typical House
Net Carbon Emission (kg C)
2000
1500
1000
Timber
Steel
Concrete Slab
500
0
-500
-1000
-1500
House Frame
Floor
Wall
Source: Honey and Buchanan, Department of Civil Engineering, University of Canterbury,
Christchurch, NZ, 1992.
Comparative Emissions in Manufacturing
Wood vs. Steel-Framed Interior Wall
Emission/Effluent
CO2 (kg)
CO (g)
SOX (g)
NOX (g)
Particulates (g)
VOCs (g)
Methane (g)
Wood Wall
305
2,450
400
1,150
100
390
4
Steel Wall
965
11,800
3,700
1,800
335
1,800
45
Source: Athena Sustainable Materials Institute, 1993.
Comparative Effluents in Manufacturing Wood
vs. Steel-Framed Interior Wall
Emission/Effluent
Wood Wall
Suspended solids (g)
12,180
Non-ferrous metals (mg)
62
Cyanide (mg)
99
Phenols (mg)
17,715
Ammonia (mg)
1,310
Halogenated
organics (mg)
507
Oil and grease (mg)
1,421
Sulphides (mg)
13
Steel Wall
495,640
2,532
4,051
725,994
53,665
20,758
58,222
507
Source: Athena Sustainable Materials Institute, 1993.
It all comes down to this:
Although periodic harvesting of
forests is viewed as environmentally
undesirable in some circles, failure to
responsibly harvest triggers a number
of undesirable environmental impacts.
These impacts are often quite
substantial.
Options to Domestic Harvest of
Timber
• Shift to use of raw materials other than
wood.
• Use wood, but import needs.
• Reduce the rate of raw material
consumption/recycle.
Shift to Non-Wood Raw Materials
• A massive substitution would be
necessary to significantly impact wood
use.
• Needs are already largely imported.
• Gathering and processing of potential
substitute materials is relatively energy
intensive, with large environmental
impacts.
Use Wood, But Import Needs
Importing Raw Material Needs as a
National Environmental Strategy . . .
• Is unethical
• Has adverse implications for
– Global environment
– Balance of trade
– Long term economic security
Reduce the Rate of Raw Material
Consumption . . .
Probably a good idea, at least in U.S., but . .
• World population is likely to double within
the relatively near term
• Large segments of the world population are
seeking to consume more, not less.
• Population gains in developing countries
translate to relatively larger increases in
demand for raw materials.
Summary
Summary
• Substantial increases in population are
certain.
• Substantial increases in global raw material
demand will occur.
• Competition for basic raw materials will
continue to increase.
Summary
• Figuring out how to provide a billion
new housing units for a growing
population while also protecting the
environment will a non-trivial
undertaking.
Summary
• Wood will be clearly be an important part
of the sustainability equation. In fact, for
the sake of the environment, a strong
case can be made that we should use as
much wood as possible.