SRC-009

Avoiding greenwash in reporting life cycle greenhouse gas emissions of space solar power: environmentally-extended input-output versus process-based approaches

Published claims resting on this source

• CLM-0182 When two different research teams assessed the exact same 1978 space solar power design, the older accounting method (which spreads emissions across whole economic sectors) found about 20 grams of CO2 per kWh, while a newer, more detailed method that traces actual physical processes found 5 to 6 times more - showing that the choice of carbon-accounting method and what it covers can swing a headline SBSP carbon number by a factor of five or six.
• CLM-0825 The authors argue that the cost-based way of estimating carbon is too coarse for a custom-built industry like spacecraft, and they conclude that their own materials-and-process method should be preferred for space studies.
• CLM-0826 When the authors redid NASA's own 2024 figures for two satellite designs using their materials-based method instead of NASA's cost-based one, the carbon per unit of electricity came out about 11 to 18 per cent lower, and they say this suggests NASA's published figures for these two designs are too high.
• CLM-0827 The authors say NASA's 2024 carbon figures for two satellite designs came out of a model built on NASA's own cost estimates, and that NASA had not used this kind of model for a space solar power study in roughly twenty years, a period in which European researchers had developed methods NASA's assessment did not draw on.
• CLM-0828 The authors say ESA's own space life-cycle guidance advises against the cost-based method because it tends to overstate environmental impact, and the authors then add that the same method's lower level of detail can also cause it to understate impact.
• CLM-0829 The authors leave alumina, black carbon and water vapour from rocket exhaust out of their own carbon study because the atmospheric effects are too uncertain to quantify, even though in an earlier study of theirs almost all of the ozone damage came from exactly those launch emissions.
• CLM-0830 The authors say an environmental claim about a space technology counts for nothing unless a proper standardised life-cycle study backs it, and that whoever makes the claim should be able to hand the evidence to anyone who asks without making it hard to get.
• CLM-0831 This is a conference paper from October 2024 that does not claim to have been independently peer reviewed, states that it calculated no uncertainty figures, and argues it did not need the independent review that the life-cycle standards normally ask for because it says it is comparing methods rather than making an environmental claim.
• CLM-0853 The wide range of published carbon figures for space solar power is not simply disagreement: most of it separates into two causes, which calculation method was used and which satellite design was assessed, and the method effect does not even point the same way in every case. The lowest published figure also counts carbon dioxide alone, while the others count all greenhouse gases, so part of the spread is a difference in what was counted.
• CLM-0849 The range of 13 to 43 grams that NASA compares its satellites against comes from one US laboratory's dataset, and the two ends are the middle values for two different technologies, wind and solar, not the spread of possible values for either.
• CLM-1462 (low confidence) A 2020 paper's finding that its detailed method gave five to six times the carbon of an earlier, simpler study of the same 1978 design compares a carbon-dioxide-only figure with a figure that also counts other greenhouse gases, and the paper labels the earlier figure two different ways in two places.

Cite this