2 results
Search Results
Now showing 1 - 2 of 2
- ItemImpacts of enhanced weathering on biomass production for negative emission technologies and soil hydrology(Katlenburg-Lindau [u.a.] : Copernicus, 2020) De Oliveira Garcia, Wagner; Amann, Thorben; Hartmann, Jens; Karstens, Kristine; Popp, Alexander; Boysen, Lena R.; Smith, Pete; Goll, DanielLimiting global mean temperature changes to well below 2 Ā°C likely requires a rapid and large-scale deployment of negative emission technologies (NETs). Assessments so far have shown a high potential of biomass-based terrestrial NETs, but only a few assessments have included effects of the commonly found nutrient-deficient soils on biomass production. Here, we investigate the deployment of enhanced weathering (EW) to supply nutrients to areas of afforestation-reforestation and naturally growing forests (AR) and bioenergy grasses (BG) that are deficient in phosphorus (P), besides the impacts on soil hydrology. Using stoichiometric ratios and biomass estimates from two established vegetation models, we calculated the nutrient demand of AR and BG. Insufficient geogenic P supply limits C storage in biomass. For a mean P demand by AR and a lowgeogenic-P-supply scenario, AR would sequester 119 Gt C in biomass; for a high-geogenic-P-supply and low-AR-Pdemand scenario, 187 Gt C would be sequestered in biomass; and for a low geogenic P supply and high AR P demand, only 92 GtC would be accumulated by biomass. An average amount of ā¼ 150 Gt basalt powder applied for EW would be needed to close global P gaps and completely sequester projected amounts of 190 Gt C during the years 2006-2099 for the mean AR P demand scenario (2-362 Gt basalt powder for the low-AR-P-demand and for the high-AR-P-demand scenarios would be necessary, respectively). The average potential of carbon sequestration by EW until 2099 is ā¼ 12 GtC (ā¼ 0:2-ā¼ 27 Gt C) for the specified scenarios (excluding additional carbon sequestration via alkalinity production). For BG, 8 kg basaltm2 a1 might, on average, replenish the exported potassium (K) and P by harvest. Using pedotransfer functions, we show that the impacts of basalt powder application on soil hydraulic conductivity and plant-Available water, to close predicted P gaps, would depend on basalt and soil texture, but in general the impacts are marginal. We show that EW could potentially close the projected P gaps of an AR scenario and nutrients exported by BG harvest, which would decrease or replace the use of industrial fertilizers. Besides that, EW ameliorates the soil's capacity to retain nutrients and soil pH and replenish soil nutrient pools. Lastly, EW application could improve plant-Available-water capacity depending on deployed amounts of rock powder - adding a new dimension to the coupling of land-based biomass NETs with EW. Ā© 2020 Royal Society of Chemistry. All rights reserved.
- ItemThe limits to global-warming mitigation by terrestrial carbon removal(Hoboken, NJ : Wiley, 2017) Boysen, Lena R.; Lucht, Wolfgang; Gerten, Dieter; Heck, Vera; Lenton, Timothy M.; Schellnhuber, Hans JoachimMassive nearāterm greenhouse gas emissions reduction is a precondition for staying āwell below 2Ā°Cā global warming as envisaged by the Paris Agreement. Furthermore, extensive terrestrial carbon dioxide removal (tCDR) through managed biomass growth and subsequent carbon capture and storage is required to avoid temperature āovershootā in most pertinent scenarios. Here, we address two major issues: First, we calculate the extent of tCDR required to ārepairā delayed or insufficient emissions reduction policies unable to prevent global mean temperature rise of 2.5Ā°C or even 4.5Ā°C above preāindustrial level. Our results show that those tCDR measures are unable to counteract ābusinessāasāusualā emissions without eliminating virtually all natural ecosystems. Even if considerable (Representative Concentration Pathway 4.5 [RCP4.5]) emissions reductions are assumed, tCDR with 50% storage efficiency requires >1.1āGha of the most productive agricultural areas or the elimination of >50% of natural forests. In addition, >100āMtN/yr fertilizers would be needed to remove the roughly 320āGtC foreseen in these scenarios. Such interventions would severely compromise food production and/or biosphere functioning. Second, we reanalyze the requirements for achieving the 160ā190āGtC tCDR that would complement strong mitigation action (RCP2.6) in order to avoid 2Ā°C overshoot anytime. We find that a combination of high irrigation water input and/or more efficient conversion to stored carbon is necessary. In the face of severe tradeāoffs with society and the biosphere, we conclude that largeāscale tCDR is not a viable alternative to aggressive emissions reduction. However, we argue that tCDR might serve as a valuable āsupporting actorā for strong mitigation if sustainable schemes are established immediately.