New Feed Sources Key to Ambitious Climate Targets
B. Walsh, F. Rydzak, A. Palazzo, F. Kraxner, M. Herrero, P.M. Schenk, P. Ciais, I. A. Janssens, J. Peñuela, A. Niederl-Schmidinger and M. Obersteiner
1960 1980 2000 2020 2040 2060 2080 2100
−10
−5 0 5 10 15 20 25 30
1et EPissiRns [3gC y−1 ]
12.4 3gC y−1
4.5 3gC y−1 0.9 3gC y−1
-3.1 3gC y−1 -6.7 3gC y−1
BA8
BiREneUgy Alg-Fuel Alg-Feed
Alg-Feed CC625 Alg-Feed CC650
Alg-Feed CC675 CDIAC DDtD 5C3 2.6 5C3 4.5 5C3 6.0 5C3 8.5
Algal feedstock can free the arable land necessary to transform the energy and land use sectors into
net carbon sinks, precipitating returns to preindustrial atmospheric carbon levels and temperatures by 2100.
Looming Challenges
• Huge Productivities: up to 150 tDM/ha/y in closed systems
• Minimal Resource Loads: can be produced on degraded or unproductive land in salt and brackish water with flue gas and waste water.
• Good for Animals: demonstrated up to 45%
of ruminant diets without effect on feed palatability, animal growth, or mortality.
• Great Value: meeting 40% of feed demand in 2013 would have cost 250-920 B$US ($500 –
$1840 / tDM).
• For comparison, global fossil fuel subsidies were 550 B$US in 2013.
• Algae closes critical carbon, water, and fertilizer cycles and therefore avoids the
tradeoffs and problem shifting we see with other biofuels
Land Use & Energy
1960 1980 2000 2020 2040 2060 2080 2100
200 300 400 500 600 700 800 900
AtPRsSheUiF C2 2 [SSP]
624 ppm
473 ppm 417 ppm 359 ppm 310 ppm
BA8
BiREneUgy AOg-FueO AOg-Feed
AOg-Feed CC625 AOg-Feed CC650
AOg-Feed CC675 CDIAC DDtD 5C3 2.6 5C3 4.5 5C3 6.0 5C3 8.5
1900 1950 2000 2050 2100
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
∆7 fURP 3UHindustUiDl [◦ C]
5C3 2.6 5C3 4.5
5C3 6.0 2.8◦C
2.1◦C 1.8◦C 1.4◦C 1.0◦C BAU
BiREnHUgy Alg-FuHl Alg-FHHd
Alg-FHHd CC625 Alg-FHHd CC650 Alg-FHHd CC675 HDdC5U74 DDtD
1900 1950 2000 2050 2100
0 200 400 600 800 1000
%A8 PUiPDUy (nHUJy [(J y−1 ] G(A
145 EJ 102 EJ 212 EJ 58 EJ 166 EJ 124 EJ 26 EJ
)ossiO )uHOs
0DUNHW 6hDUH 91% 89% 85% 77% 68% 57%
PUiPDUy (nHUJy DHPDnG HisWoUiFDO DDWD (I(A)
%ioPDss CoDO GDs 1uFOHDU 2iO
6oODU WinG
1900 1950 2000 2050 2100
0 200 400 600 800 1000
AOJ-FHHG 3riPDry EnHrJy [E- y−1 ]
446 EJ 25 EJ 100 EJ
58 EJ 0 EJ 201 EJ
48 EJ
FossiO FuHOs
0DrNHW 6hDrH 91% 88% 70% 36% 20% 14%
EnHrJy DHPDnG IEA DDWD
AJro-%ioPDss
&oDO GDs
1uFOHDr & HyGro.
2iO 6oODr WinG
2.0 2.5 3.0 3.5 4.0 4.5
3eUP. 3astuUes & 0eadRws [Bha]
3.9 Bha
2.5 Bha BA8
BLREneUgy AOg-FueO
AOg-Feed FA26TAT
1.0 1.2 1.4 1.6 1.8 2.0
AUaEOe Land & 3eUP. &URSs [Bha]
1.8 Bha
1.4 Bha
1950 2000 2050 2100
0.0 0.5 1.0 1.5 2.0 2.5
6hRUt 5RtatLRn &RSSLFe [Bha]
0.8 Bha 2.0 Bha
Algae as Feedstock
• Climate Change: to limit warming below 2C, net emissions must be reduced to zero by 2075.
• Protein Shortfall: economic &
demographic growth combine to increase vegetal (+80%) and animal food demand (+120%) by 2100.
• Land Scarcity: food demand growth
could outstrip agricultural intensification, driving land use change and exacerbating emissions & biodiversity loss.
• Water Scarcity: climate change and agricultural intensification will drive
expansion of irrigation, depleting aquifers.
• Nutrient Cycling: agricultural runoff and other wastewater drive eutrophication and pollute surface and ground water.
Using microalgae to meet 40% of global animal feed demand (2010: 0.5 Gt/y; 2100: 1.0 Gt/y) would free almost 2 Bha of arable land, which could be used for energy crop production.
