Table 1.

Carbon production intensities and sequestration potential of highly alkaline materials, by-products and wastes

Material	2010 CO2 intensitya	2050 CO2 intensityb	Carbonation potentialc	Measured carbonationd	Enhanced weathering potentiale	Carbon offset recycling/reusef
Blast furnace slag	12,000	2700–4300 (286–1080)i	413 ± 13	90–230	620 ± 19	~100. Up to 700 in high substitution specialised cements. <5 as aggregate
Basic oxygen furnace slag			402 ± 17	50–540	602 ± 25
Electric arc furnace slag			368 ± 10		552 ± 15
Ordinary portland cement	800	200–400 (100–200)i	510	300	773	—
Cement kiln dust	6900g	1700–3500	330 ± 12	82–260	530 ± 21	~0 Recycled into kiln
Construction and demolition waste	—	—	77–110	—	110–190	<5 As aggregate
Lime	1000	200h	777 ± 13	—	1165 ± 19	—
Ultrabasic mine tailings	8–250	—	40–250	<50	60–377	—
Hard coal ash	20,000	(2000–2600)i	36 ± 6	20–30	73 ± 10	~100. Up to 700 in high substitution specialised cements
Lignite ash			146 ± 28	230–264	246 ± 52
Marine algae biomass ash	490	<−16,200	31	—	348
Wood/woody biomass ash			−89–815	80–380	−118 to 1766
Herbaceous and agricultural biomass ash			−239–520		−323 to 1505
Animal biomass ash38			56–376	—	145–724
Biomass average			186 ± 126	—	461 ± 260
Red mud	5400	(1080)	47 ± 8	7–53	128 ± 18 < 440 with acid neutralising capacity of liquor	—

Input data are presented in Supplementary Table 2 and Supplementary Note 1, all units in kg CO₂ t⁻¹

^aCalculated by dividing the emissions of the production process by the mass of alkaline material

^bPredicted future emission normalised to mass of alkaline material

^cMaximum CO₂ capture potential by forming carbonate minerals

^dCO₂ capture measured in experimental work

^eMaximum enhanced weathering CO₂ capture potential

^fCO₂ mitigation potential from other uses of material

^gSee Supplementary Notes 2 and 3

^hBased on an 80% emission reduction target²⁶ (e.g., UK and EU)

ⁱAccounting for aggregate primary energy carbon intensities in RCP2.6 by 2050. Brackets denote 2100 projected