Increased carbon capture by a silicate-treated forested watershed affected by acid deposition


Lyla L. Taylor1, Charles T. Driscoll2, Peter M. Groffman3,4, Greg H. Rau5, Joel D. Blum6, and David J. Beerling1

1Leverhulme Centre for Climate Change Mitigation, Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK

2Department of Civil and Environmental Engineering, 151 Link Hall, Syracuse University, Syracuse, NY 13244, USA

3City University of New York, Advanced Science Research Center at the Graduate Center, New York, NY 10031, USA

4Cary Institute of Ecosystem Studies, Millbrook, NY 12545, USA

5Institute of Marine Sciences, University of California, Santa Cruz, CA 95064, USA

6Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109, USA

In addition to reducing emissions, nations aiming to meet their agreed targets to mitigate climate change will need to employ Carbon Dioxide Removal (CDR) strategies. One such strategy is Enhanced Rock Weathering (ERW) which relies on CO2 dissolved in rainwater, which forms carbonic acid and chemically attacks mineral surfaces.  If the minerals contain “base cations” such as calcium,  soil pH will rise and more carbon dioxide will dissolve, to be transported downstream and stored in the oceans. Note that this process is less efficient if the rocks being weathered already contain CO2, such as limestone.  Such rocks can become a source of CO2, so CO2-free silicate minerals are preferred.
Base cations liberated from the rocks being weathered are also nutrients for plants. In the Hubbard Brook Experimental Forest, acid rain had led to leaching of calcium with adverse effects on sugar maples, so relatively small quantities of silicate mineral pellets were applied to an entire watershed in 1999 in an attempt to replace that calcium and improve forest health. Unwittingly, this comprised one of the earliest watershed-scale ERW experiments, and there is a wealth of data available to assess its impacts.
The experiment led to an improvement in the productivity and health of sugar maples in this forest, leading to sequestration of carbon in the wood and a small increase in dissolved CO2 transported downstream.  We aimed to build a greenhouse gas budget for the forest, measuring the amount of calcium and dissolved CO2 that had been transported downstream, the increase in wood storage, any organic carbon lost in streamwater, and also any greenhouse gas emissions from the soil and streams, including carbon dioxide, methane and nitrous oxide. Despite initial penalties due to release of an estimated 0.8-2.4 metric tons of CO2 during mining, grinding, road transport and use of a helicopter to spread the minerals on the forest, this watershed appears to have sequestered more carbon than an untreated nearby reference watershed: 8.5-11.5 metric tons of CO2 net per hectare over a 15-year period. In this case, the improved wood production was the main sink for carbon. These results suggest that similar acid-impacted forests would benefit from such treatments from a climate change perspective given sustainable sources of rock dust.

Tensions in the energy transition: Swedish and Finnish company perspectives on bioenergy with carbon capture and storage

Tensions in the energy transition: Swedish and Finnish company perspectives on bioenergy with carbon capture and storage

Authors: Emily Rodriguez, Adrian Lefvert, Mathias Fridahl, Stefan Grönkvist, Simon Haikola, and Anders Hansson


Rodriguez, E., Lefvert, A., Fridahl, M., Grönkvist, S., Haikola, S. and Hansson, A., 2021. ‘Tensions in the energy transition: Swedish and Finnish company perspectives on bioenergy with carbon capture and storage’, J. Clean. Prod., 280. 10.1016/j.jclepro.2020.124527


Sweden and Finland have national goals to reach net negative greenhouse gas emissions before mid-century. Achieving these ambitious goals could employ negative emission technologies, such as bioenergy with carbon capture and storage, but it is unclear how this technology could be realized in an energy transition. Sweden and Finland stand out for having a large share of substantial point source emissions of biogenic carbon dioxide, in the production of pulp, heat and power. In the European Pollutant Release and Transfer Register, Sweden and Finland reported 64% and 51% biogenic emissions, respectively, in facilities emitting over 100 kt of carbon dioxide in 2017, while the corresponding collective figure for all European states in the database is 6%. This qualitative study highlights company actors’ perspectives on bioenergy with carbon capture and storage within a Nordic regional context and explores their perspective on emerging tensions in the energy transition. Semi-structured interviews were conducted with 20 of the 24 companies with the largest point sources of biogenic emissions. The results are framed around four emerging tensions regarding bioenergy with carbon capture and storage from companies’ perspectives in this study: (1) absence of reliable long-term policies; (2) limits to companies’ climate change responsibility; (3) technical trade-offs of carbon capture; and (4) lack of customer demands for negative emissions. According to most of the companies, it is technically feasible to capture carbon dioxide, but it could be a challenge to determine who is responsible to create a financially viable business case, to enact supporting policies, and to build transport and storage infrastructure. Company representatives argue that they already contribute to a sustainable society, therefore bioenergy with carbon capture and storage is not their priority without government collaboration. However, they are willing to contribute more and could have an increasing role towards an energy transition in an international context.

Negative Emissions and The Long History of Carbon Removal

Authors: Wim Carton, Adeniyi Asiyanbi, Silke Beck, Holly J. Buck, Jens F. Lund

Prepared for the Institute for Carbon Removal Law and Policy

Recent IPCC assessments highlight a key role for large-scale carbon removal in meeting the objectives of the Paris Agreement. This focus on removal, also referred to as negative emissions, is suggestive of novel opportunities, risks, and challenges in addressing climate change, but tends to build on the narrow techno-economic framings that characterize integrated assessment modeling. While the discussion on negative emissions bears important parallels to a wider and older literature on carbon sequestration and carbon sinks, this earlier scholarship—particularly from the critical social sciences—is seldom engaged with by the negative emissions research community. In this article, we survey this “long history” of carbon removal and seek to draw out lessons for ongoing research and the emerging public debate on negative emissions. We argue that research and policy on negative emissions should proceed not just from projections of the future, but also from an acknowledgment of past controversies, successes and failures. In particular, our review calls attention to the irreducibly political character of carbon removal imaginaries and accounting practices and urges acknowledgment of past experiences with the implementation of (small-scale) carbon sequestration projects. Our review in this way highlights the importance of seeing continuity in the carbon removal discussion and calls for more engagement with existing social science scholarship on the subject. Acknowledging continuity and embracing an interdisciplinary research agenda on carbon removal are important aspects in making climate change mitigation research more responsible, and a precondition to avoid repeating past mistakes and failures.

Ambient Weathering Magnesium Oxide For Co2 Removal From Air

Authors: Noah McQueen, Peter Kelemen, Greg Dipple, Phil Renforth, Jennifer Wilcox

Full Citation: McQueen, N., Kelemen, P., Dipple, G., Renforth, P., and Wilcox, J. Ambient weathering of magnesium oxide for CO2 removal from air. Nat Commun 11, 3299 (2020).

Updated Abstract: 

To combat the dangerous effects of climate change, new technologies are needed to remove billions of tonnes of carbon dioxide (CO2) from the atmosphere. This paper analyzes the cost of a land-based process that uses a magnesium carbonate (magnesite, MgCO3) feedstock to repeatedly capture CO2 from the atmosphere. 

In this process, the initial magnesium carbonate feedstock is fed into a high temperature reactor, called a calciner. In the calciner, the magnesium carbonate is heated to produce magnesium oxide (MgO) and CO2, which is subsequently captured. The produced MgO is highly reactive with the CO2 in air; at ambient conditions, the MgO and CO2 react to re-produce magnesium carbonate materials. This high reactivity means the MgO can be transported to plots of land and used to naturally uptake CO2 from the ambient air. At the end of one year, the MgO will have reacted with CO2 to form magnesium carbonates. From here, the magnesium carbonates are transported back to the calciner, where they are once again heated to re-produce the MgO and release the atmospheric CO2 as a high-purity CO2 stream which can then be captured and stored or utilized. The process can then continue cyclically, making up for any losses by adding new MgCO3 into the calciner. 

Using an exploratory economic analysis, we estimate that this process could cost approximately 45 to 193 USD per tonne of CO2 captured from the air, considering the use of grid or solar electricity. The thermal energy for this process is provided by natural gas, which is combusted inside the calciner in pure oxygen, allowing for the co-capture of combustion-related CO2. The cost range presented here is large mainly on account of varying process parameters and uncertainty in the capital expenses.

This cyclical technology may achieve lower costs than optimistic projections for other direct air capture methods and has the scalable potential to remove 2 to 3 billion tonnes of CO2 per year, and thus may make a meaningful contribution to mitigate global warming.

Managing Land‐based CDR: BECCS, Forests and Carbon Sequestration

Duncan Brack, Richard King

doi: 10.1111/1758-5899.12827


Decisions about when, where and how to achieve widespread carbon dioxide removal (CDR) are urgently required. Delays in developing the requisite policy and regulatory frameworks increase the risks of overshooting climate goals and will necessitate much larger negative emissions initiatives in the future. Yet the deployment of bioenergy with carbon capture and storage (BECCS) at the scales assumed under most ParisAgreementcompliant emissionreduction pathways is unlikely. More generally, the sustainability of largescale BECCS is questionable given its extensive land, water, and energy requirements for feedstocks and the competing necessity of these resources for the provision of ecosystem services and attainment of multiple Sustainable Development Goals. BECCS on a more limited scale, however, could have more benign impacts if feedstocks were restricted to wastes and residues. There is also widespread recognition that extensive afforestation, reforestation and forest restoration have critical roles in reducing greenhouse gas emissions to net zero. To date there has been little focus on the optimum strategies for integrating landbased CDR approaches – under which circumstances forest areas are best left undisturbed, managed for conservation, and/or managed for harvested wood products, and how these options affect the availability of residual feedstocks for BECCS. This paper reviews this debate and suggests appropriate policy measures.

Three principal policy implications emerge:

First, the necessity of abandoning the assumption, common in integrated assessment models, that BECCS is the preeminent carbon removal solution. Rather it needs to be analysed alongside all other negative emissions technologies (NETs), on the basis of full lifecycle carbon balances (including dropping the assumption that biomass feedstock is inherently carbonneutral), as well as other ecosystem and sustainability cobenefits and tradeoffs.

Second, urgent action is required to scale up the development and deployment of sustainable NETs. No single NET – whether BECCS, naturebased, or otherwise – will achieve the scale of CDR required in the vast majority of 1.5°C and 2°C mitigation scenarios, let alone do so sustainably. But portfolios of multiple NETs, deployed sensitively at modest scales, will be invaluable for achieving climate security. This requires designing policy and financial mechanisms that are sufficiently attuned to the contextual specificities of each potential deployment, but which are sufficiently catalytic to galvanise appropriate and complementary actions at adequate scales and with enough urgency.

Third, we need to be absolutely clear that all CDR efforts have to be additional to – not substituting for, or detracting from – urgent acceleration of conventional abatement actions. This means we need to accelerate conventional abatement action as rapidly as possible. There are too many drawbacks and uncertainties associated with BECCS and other NETs to place excessive reliance on them – though carbon removal solutions will undoubtedly be needed.

The Potential of Carbon Capture and Sequestration in the Northeast and Mid-Atlantic regions

The International Panel on Climate Change cites the widespread deployment of carbon capture and sequestration (CCS), bioenergy, and/or their combination (BECCS) as critical to the effort to limit 21st century warming due to CO2 release. The removal of CO2 from industrial effluent streams and storage in geological formations (CCS), is an established mitigation strategy that has the potential to decrease the rate at which CO2 is emitted into the atmosphere. More importantly, it is a technology that can progress towards achieving negative emissions through coupling CCS with CO2 capture from electricity generation processes driven by the combustion of biomass (BECCS). BECCS is particularly appealing because it addresses how electricity could be produced in a carbon negative future.

In “Total Cost of Carbon Capture and Storage Implemented at a Regional Scale: Northeastern and Midwestern United States” (Schmetz, Hochman & Miller, 2020), the authors show that CO2 emissions may be stored at the Northeast and Mid-Atlantic regions of the US at $52 per ton, sourced from coal-fired plants and stored onshore in depleted oil and gas fields, and that the region also has the opportunities to store CO2 in onshore saline reservoirs for less than $60 per ton. Offshore storage is also an option, where the lowest total costs of CCS with storage in offshore saline reservoirs are just over $60 per ton. Storage offshore carries less risk and inconvenience and less potential for interference from populations than onshore storage. Offshore storage could also be required if formation pressures pose geological risk issues when injecting gigatons of supercritical CO2 into onshore formations. Emissions from natural-gas-fired plants are more expensive to capture per ton of CO2, making the lowest total costs over $80 per ton. This analysis suggests that a relatively small (15%) reduction in the total cost of CCS, would make CCS economically viable at a large-scale (~8 Gt CO2 over 30 years). Large-scale carbon storage may be additionally justified when coupled with BECCS technology. Similarly, demonstrating the feasibility of CCS could ultimately facilitate a pathway to BECCS.

Enacted in 2018 by the 115th United States Congress, the Section 45Q tax credits allot $50 per ton CO2 in tax credits for the permanent sequestration of CO2 in saline geological formations, as well as $35 per ton CO2 for EOR applications of CCS. To this end, the difference between representative total costs of CCS in the northeastern and midwestern United States and the threshold for profit motivated adoption is relatively small with the Section 45Q credits. With some technological improvement, adoption of CCS on a meaningful scale is possible in this region. With EOR and 45Q, CCS is viable, and has been undertaken on commercial scales at the Petra Nova-WA Parish Generating Station in Texas and the Boundary Dam plant in Canada. CO2 captured at both of these locations is transported to nearby oil fields and sold to enhance recovery. Governments can and should support these initiatives as sound environmental policy, like the U.S. and Canadian federal governments did for Petra Nova and Boundary Dam, providing $190 million and $240 million for those projects, respectively. Grant funding supporting the construction of commercial scale CCS projects, like the $190 million DOE supplied for the Petra Nova plant, incentivize first-of-a-kind construction that allows for learning, feasibility testing, and risk reduction for future commercial implementations. The 45Q tax credit incentive is a promising environmental policy initiative that encourages the adoption of CCS, the reduction of its cost over time because of learning-by-doing and could ultimately result in reduction of CO2 in the atmosphere.

 Considering the risk and long-term planning and capital commitment associated with constructing or renovating electricity generating infrastructure to serve CCS, the initiative to incentivize early CCS applications should also be coupled with a long-term commitment to the section 45Q credits. If the political support for CCS and the section 45Q credits appears fragile or short-lived, the potential repeal or expiration of these credits will become a hazard that adds to the risk prospective CCS adopters will need to account for. This short-term commitment coupled with the energy infrastructure risk paradigm could nullify the incentives for adoption of carbon capture technology that the Section 45Q tax credits were written to provide.

While the establishment of CCS must precede full-scale implementation of BECCS from a logical/technological perspective, concurrent pilot projects that demonstrate the feasibility of BECCS would represent significant advances. One such opportunity for CCS and BECCS could come in the form of power plants that are facing pressure to refuel or repower with more environmentally sound technology, such as the to-be-shuttered coal-fired B.L. England Generating Station in southern New Jersey. The plant was scheduled for a conversion to natural gas, but successful opposition to a pipeline link resulted in the cancellation of the project. A conversion to biomass, perhaps co-firing with coal, coupled with carbon capture could presumably ameliorate the environmental concerns that comprised the original basis for shuttering the plant. Additionally, this plant, and other legacy coal-fired locations, is served by a railroad infrastructure that would make transporting biomaterials to the plant for co-firing with coal a simple transition that does not require traversing the complexities of constructing new pipeline. This particular location, as well as a couple others on the U.S. East Coast, is well-suited for carbon storage with reservoirs available both below the power-plant and in nearby regions offshore that would encounter less citizen opposition. A project of this nature could represent an example of a catalytic “tangible, near-term success” for CCS, biomass, and/or BECCS. Application of BECCS technology in a state like New Jersey that lacks an oil and gas culture and history and is strongly opposed to further industrialization including pipelines might provide a viable test for addressing concerns about BECCS and aid in the transformation from coal to renewable, carbon negative BECCS technology.


Schmelz, William J., Gal Hochman, and Kenneth G. Miller. “Total cost of carbon capture and storage implemented at a regional scale: northeastern and midwestern United States.” Interface Focus 10.5 (2020):


A critical overview of solar assisted carbon capture systems: Is solar always the solution?

Mohammad Saghafifar, Samuel Gabra                                                                  International Journal of Greenhouse Gas Control, 2020

This paper focuses on possible integration schemes between solar thermal collectors and carbon capture systems. In its entirety, solar assisted carbon capture systems can be categorized into direct and indirect systems. Key factor in designing solar assisted carbon capture systems
is to match the thermal-grade between the collector and gas separation process.

For post-combustion systems, in particular, amine based systems have been widely considered for integration with solar thermal collectors using either direct or indirect schemes. Comparing direct and indirect integration schemes, results are overwhelmingly in favour of indirect solar integrations. The key merits of indirect integration include its additional flexibility in system operation and the high solar energy utilization factor it offers. For direct systems, solar thermal energy utilization is limited to the reboiler heat duty. Moreover, higher temperature concentrating solar thermal collectors with higher optical efficiencies can be used in indirect systems. These conclusions can be extended to the case of using any other low temperature gas separation technique including other chemical absorption and chemical/physical temperature swing adsorption. Direct integration may only be suitable when high grade heat is required for gas separation, as in calcium looping.

For pre-combustion systems, all the available studies focused on utilizing solar thermal energy for fuel reforming/gasification stage. It is more feasible to supply the H2/CO2 separation energy from other low-grade sources. The advantage of these systems is the inherent ability of storing solar energy chemically in form of the upgraded fuel. In addition, high-grade heat needed for reforming/gasification stage makes solar assisted systems more feasible.

For oxyfuel combustion, both direct and indirect schemes were studied. In direct systems, solar energy is used to derive an endothermic reduction reaction for chemical looping processes. Solar hybrid chemical looping systems have two advantages: first, the inherent carbon dioxide sequestration and second, storing solar thermal energy both chemically and sensibly. For indirect systems, solar energy is utilized within the power cycles whilst air separation systems were used for pure oxygen production. In terms of merits, these systems are similar to indirect systems using low temperature gas separation methods. Possible future research direction for solar assisted carbon capture systems can be classified into solar collectors cost reduction research and innovative integration scheme research. Firstly, the cost of collectors, irrespective of technology, must be reduced. In addition, more research must be carried out on high temperature solar collector integration within high-temperature carbon capture and storage (CCS) systems. For post-combustion systems, ongoing research on solar assisted calcium looping systems is promising. Integrating high-grade solar energy for fuel reforming and gasification in pre-combustion CCS is another potential research route.

An interesting aspect of solar assisted CCS systems is the possibility of its utilization as an energy storage scheme coupled with CO2 capture. In these schemes, extra available solar energy during high insolation periods is employed to further run the endothermic part of the CCS
process and store the product for usage during instances of low solar insolation. The products from these processes can be simply stored.

Fuel out of Thin Air: CO2 Capture from Air and Conversion to Methanol

Authors: Raktim Sen, Alain Goeppert, Sayan Kar, G. K. Surya Prakash*Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, Los Angeles, California, United States.

Full citation: Sen, R.; Goeppert, A.; Kar, S.; Prakash, G. K. S., Hydroxide Based Integrated CO2 Capture from Air and Conversion to Methanol. Journal of the American Chemical Society 2020, 142, 4544-4549.

Over the past two centuries, surging greenhouse gas emissions have led to an enormous rise in atmospheric CO2 levels, causing a significant increase in the average global temperature and ocean acidification. Humankind is now releasing every year > 36 billion tons of CO2 to the environment! Among various solutions explored to mitigate this problem, direct air capture (DAC) of CO2 is highly promising. DAC has significant advantages. It enables the point of capture to be independent from the emission sources. It also targets CO2 emissions from dispersed point sources, which are responsible for about half of total anthropogenic emissions but would otherwise be difficult to address. Furthermore, utilization of the captured CO2 (Carbon Capture and Utilization, CCU) as a carbon source for various chemical feedstocks and polymeric materials is very promising. In this context, CO2 is combined with hydrogen obtained by electrolysis of water using renewable energy sources such as solar and wind. Among various CO2 hydrogenation products, methanol is one of the most attractive and versatile alcohol. Methanol is a feedstock for a multitude of chemicals and products, already used on a scale of over 100 billion liters per year. Additionally, methanol, which is a liquid with a boiling point of 64.7 °C, is a superior fuel for internal combustion engines and fuel cells, as well as a convenient high density liquid hydrogen carrier. Methanol can be converted to ethylene and propylene through the MTO (methanol to olefins) process. Hence, the production of renewable methanol and the associated methanol economy holds significant potential to replace current fossil fuel-based economies.

Following the legacy of their late colleague Nobel Laureate George Olah, a major proponent of the methanol economy, G. K. Surya Prakash, professor and director at Loker Hydrocarbon Institute and his team including senior research scientist, Alain Goeppert have successfully combined the two steps of CO2 capture and hydrogenation to methanol into a seamless reaction sequence to transform the greenhouse gas into its combustible cousin. Until now, the integrated capture and conversion processes relied on organic bases called amines to capture CO2. While amines are easily regenerable, they are prone to oxidative degradation and suffer from notable toxicity and volatility. Hence, in order to improve the system, Prakash and his team turned to inorganic bases like sodium/potassium hydroxides which are superior CO2 capturing agents forming their respective bicarbonates/carbonates. Conventionally, however, recycling of the base by thermally decomposing bicarbonates/carbonates requires extreme temperatures above 700 °C making the process highly energy intensive. In initial efforts by the group, CO2 captured from air by a solution of hydroxide in water was converted to formate salts. However; further hydrogenation to methanol was ineffective. 

In their current study, the authors discovered that switching water with alcohols like ethylene glycol as a reaction medium could mediate effectively the process to methanol. When air was bubbled through potassium hydroxide dissolved in ethylene glycol and the CO2-loaded solution subsequently hydrogenated in the presence of H2 and a metal catalyst, complete conversion to methanol was observed at 140 °C. Moreover, regeneration of the hydroxide base occurred at mild temperatures of 100-140 °C. Notably, a fraction of the base was deactivated in an unwanted side reaction. Currently, the researchers are aiming to minimize the side reactions to efficiently recycle the potassium hydroxide. This system offers easy integration of existing hydroxide-based CO2 scrubbing industries to utilize the captured CO2 to produce methanol, paving a way for a sustainable and carbon neutral future. As Prakash says, “All living things are primarily made of carbon and therefore carbon has to be managed. Humankind requires carbon based fuels and chemical feedstocks currently obtained from fossil fuels. Renewable methanol can easily replace fossil fuels without requiring major changes to our current chemical and transportation infrastructures.   If CO2 is a one-carbon problem, then methanol is a one-carbon solution.”

The study authored by Prakash, Goeppert and graduate assistants Raktim Sen and Sayan Kar was recently published in Journal of the American Chemical Society (DOI: 10.1021/jacs.9b12711) and also featured in C&E News ( 

What influences farmers’ decision to adopt technologies that enhance soil carbon sequestration? A case study from East Africa.

Fig. 1. A map of Africa showing the location of Kenya and Ethiopia

Authors and their affiliation

Ng’ang’a Karanja Stanley1,**, Jalang’o, Dorcas Anyango2, Girvertz Evan2 1,**International Center for Tropical Agriculture (CIAT), Sub-regional Office – Kampala, Uganda 2International Center for Tropical Agriculture (CIAT), Regional office – Nairobi, Kenya

Soil nutrient depletion limits the agricultural potential of a majority of farmers in developing countries. Technologies that enhance soil carbon can potentially increase farm productivity, income opportunities for farmers, and improve food security. Nonetheless, the adoption of, and investment in agricultural practices that build up carbon in soils is still limited among farming households in East Africa. This study examines the factors that influence the uptake of soil carbon enhancing practices among 45 and 50 smallholder farmers from selected places in Kenya and Ethiopia (Fig. 1) respectively, using secondary data that were extracted from the World Overview of Conservation Approaches and Technology (WOCAT) database. Understanding this is requisite for the government, policy experts and development partners to effectively plan, and target interventions to scale up adoption among farmers in the region.

A probit model was used to analyse the data that spanned across socioeconomic, institutional, off-farm income, technical knowhow, farmers’ perceptions, and land use characteristics that influence the adoption of technologies that have the potential of enhancing the soil carbon sequestration. The descriptive results from the data reveal that farming is dominated by women in both countries. Mixed market orientation is dominant, with a moderate wealth status of between 100 and 500 US$ for the majority of the households.  Results from the model show that both farmers’ perceptions, and socio-economic, farm level, and institutional factors significantly contribute to the decision to implement these practices. For example, smallholder farmers that reported to have perceived the net benefits and strengths of the soil carbon enhancing technologies had a higher likelihood of adopting technologies that enhance the sequestration of soil carbon in both Kenya and Ethiopia.

At the same time, off-farm income influenced the adoption of soil carbon enhancing practices positively among farmers with a moderate annual income (100-500 US$) as compared to the rich (>500US$). Farming for subsistence basis and moderate know-how of the technologies in question negatively affected adoption. Similarly, land ownership without title deeds negatively influenced adoption. The results point to the speedy need for policy measures that would promote the adoption of soil carbon enhancing practices. Interventions such as training farmers to equip them with implementation skills, and enforcing technical assistance through extension delivery would help bridge the knowledge deficiency. Encouraging farmers’ involvement in off-farm income-generating activities, and improving access to credit is also commendable. To a greater extent, farmers would be incentivized thus boosting their intake for soil carbon enhancing practices at the individual farm level.  

Keywords: Adoption, Factors, Enhances, Constrain, Soil carbon, Practices, Kenya, Ethiopia 


**Corresponding author details


Orcid number:


The technological and economic prospects for CO2 utilization and removal


Cameron Hepburn, Ella Adlen, John Beddington, Emily A. Carter, Sabine Fuss, Niall Mac Dowell, Jan C. Minx, Pete Smith & Charlotte K. Williams


Carbon dioxide utilisation – making valuable products from CO2 – is a potential way to lower the net costs of reducing emissions or of removing carbon dioxide from the atmosphere.  We review the economic and technological prospects of ten such pathways to assess scale and cost prospects in 2050. Using CO2 in chemicals, fuels, and via microalgae to make products, comprise ‘cycling’ pathways: they might reduce carbon dioxide emissions by displacing fossil fuel derived CO2 but they have limited potential for carbon dioxide removal.  Some CO2 chemicals, such as CO2 based polymers, are profitable in the present day, but CO2 based fuels are high up on the cost curve. ‘Closed’ pathways such as those involving construction materials can both utilise and remove carbon dioxide for the long term. They might be low cost, and the end-markets are large, but they have high regulatory barriers to scale.  Land-based CO2 utilisation pathways such as soil carbon sequestration, afforestation/reforestation and biochar can increase agricultural output and remove carbon dioxide. They can be characterised as ‘open’ pathways wherein the CO2 can return to the atmosphere easily, and they are relatively low cost. Using a process of structured estimation and an expert opinion survey, our assessment suggests that each of the ten pathways could scale to over 0.5 Gt carbon dioxide utilisation annually, although barriers remain substantial and resource constraints prevent the simultaneous deployment of all pathways.  Uncertainty over scaling means that there is a wide range of potential outcomes for 2050. Notwithstanding the many caveats, the potential scale of utilisation could be considerable. Much of this potential CO2 utilisation – notably in ‘closed’ and ‘open’ pathways – may be economically viable without dramatic shifts in prices. The specific assumptions of the low scenario imply an upper bound of over 1.5 Gt CO2 yr-1 at well under $100/t CO2u. For policymakers interested in climate change, these figures demonstrate the theoretical potential for correctly designed policies to incentivise the displacement of fossil fuels or the removal of CO2 from the atmosphere.