This document is intended to be a scaffold for community discourse and creation of knowledge. The version hosted on the PubPub platform (find it here, if you aren't already viewing it) allows inline commenting. We invite ideas, additional references, and constructive criticisms via inline comments. We request that citations be included to support claims made in comments when possible. We intend to publish updates to this roadmap over time, which is possible on the PubPub platform. Well-referenced comments will be incorporated into future versions of the roadmap.
Atmospheric carbon dioxide removal (CDR) is likely required at large scale to meet society's climate goals, which will require it to scale to one of the largest global industries.
CDR has grown from a niche area to a focus of expanded R&D and policy support very rapidly in the past few years. Biotechnology is among the most rapidly advancing fields of technology, and is relevant to CDR. However, the two fields currently have very little overlap or mutual collaboration.
The goal of this roadmap is to increase research, funding, and growth of community at the intersection of CDR and biotechnology.
The primary intended audiences of this roadmap are practitioners of biotechnology and/or CDR in both academia and industry; people in charge of constructing research programs/agendas; and funders of research and industry.
The roadmap has three technical parts, focused on the topics of industrial CDR using aqueous solutions, geochemical CDR, and methods for biomass-based carbon removal and storage (BiCRS).
Our analysis focuses on opportunities for biotechnology to impact the constraints on leading CDR pathways, rather than attempting to identify the most promising overall CDR pathways using biotechnology (i.e., we took a bottom-up approach). Each technical part is structured as follows:
Key concepts
Constraints on CDR technologies that may be addressable by biotechnology (not an exhaustive list)
Possible solutions through which biotechnology could alleviate the constraints.
Challenges in implementing the solutions
Recommendations for research directions that collectively enable possible biotechnology solutions to constraints on CDR technologies
Different readers may benefit from the report in different ways.
All readers may find utility in the list of recommendations given at the end of each part of the technical body of the report, as a concise call to action.
Practitioners of biotechnology may find utility in the background information on CDR pathways, descriptions of constraints, and list of possible solutions for contextualizing their talents in CDR.
Practitioners of CDR may find utility in the list of possible solutions given in the technical body of the report for identifying ways biotechnology can impact their work.
People constructing research programs/agendas and funders may find utility in the list of possible solutions given in the technical body of the report for identifying mutually-supportive research projects around which to coordinate efforts.
We recommend that efforts be made to connect the communities of climate tech (including CDR) and biotechnology, through education, research funding, and industry. In particular, grants should be made available to fund the multidisciplinary teams required to most effectively pursue the research directions discussed throughout this report.
Motivations
Climate change and decarbonization research indicates that meeting proposed climate goals will likely require removing CO2 from the atmosphere—carbon dioxide removal (CDR)—at an enormous scale, alongside rapid emissions reduction (NASEM, 2019)(Galán-Martín et al., 2021)(Shukla et al., 2022), (Friedmann, 2022), (Mazurek et al., 2022). For example, the Intergovernmental Panel on Climate Change (IPCC) estimates that CDR of 1-10 Gt CO2/yr will be needed by mid- to late- century in order to avoid warming of >2 ˚C (IPCC, 2022). To achieve such levels, CDR must scale to become one of the world's largest industries within the next few decades, on par with oil and gas today.
However, CDR technology and its downstream components are a new technology focus that is still at an early stage of development, in terms of both foundational technology and scaling (Smith et al., 2023). Innovation is needed at all levels, including foundational mechanisms, optimizations, and scaling, to develop CDR that is as reliable, cost-effective, and minimally environmentally-impactful as possible. Therefore, substantially more person-power must be brought to bear on CDR to enable innovation on the needed timescale. Further, CDR is highly interdisciplinary (Zelikova, 2020). As such, progress can be enabled by clearly mapping technology challenges in CDR to relevant disciplines.
As a contribution to that broader effort, this roadmap focuses on identifying opportunities for the discipline of biotechnology to contribute to CDR technology. Biotechnology is of special interest because it is a recently-developed field that is undergoing a revolution, and application of biotechnology to CDR is at a very early stage. Most of the opportunities we identify push the boundaries of current biotechnology capabilities. However, the 21st century has been heralded as the “century of biology,” and we should expect continued rapid development of the capabilities of biotechnology during the same timeframe as deep decarbonization of our economies and the rise and maturation of CDR. It is therefore essential to identify goals toward which biotechnology innovators should orient their efforts early on, so that novel capabilities in biotechnology may be integrated into CDR as quickly as possible.
Currently, biotechnology focuses primarily on biomedicine rather than climate, which is a result of substantially greater funding and commercial opportunity in biomedicine, both historically and today. As a result, many researchers in foundational biotechnology are developing powerful tools without a clear understanding of how they may apply to problems in climate. Fortunately, the authors have seen that many biotechnology researchers feel a growing personal motivation to address climate change and are seeking actionable work. That makes it all the more urgent to clarify impactful opportunities for biotechnology in CDR.
Simultaneously, the rapid growth and historical biomedical focus of biotechnology relative to other engineering disciplines make it especially difficult for people in the fields of CDR and broader climate tech to maintain a current understanding of its tools.
By communicating the opportunities available specifically to skillsets in biotechnology, we provide clear points of integration of the community of biologists and bioengineers with the CDR community, and guide research managers and funders within both fields in their efforts to maximize impact.
We are inspired by work from Sarah Sclarsic (Sclarsic, 2021) with the same focus.1 We have built on that work by providing deeper technical exploration of key topics. Both efforts draw inspiration from (Rolnick et al., 2019), which described opportunities for the machine learning community to contribute to addressing climate change and provided the impetus to form Climate Change AI, an organization focused on enabling the AI community to work on climate change. To our knowledge, (Sclarsic, 2021) and this roadmap are the first efforts focused on mapping opportunities for a specific engineering discipline in CDR, and to target an audience of a specific disciplinary community outside of CDR. It would be valuable to pursue similar efforts for other disciplines.
A holistic technical roadmapping effort providing in-depth exploration of research opportunities across many disciplines would be expected to produce the most impactful insights, although it would be more intellectually challenging to achieve true technical depth and actionable recommendations in such an effort.2 Integrating specific disciplines into CDR, as attempted here, should help enable future deep, multidisciplinary technical roadmapping.
Brief introduction to CDR
For humanity to depend on CDR as a component of decarbonization, CDR must meet five essential criteria. Its mechanisms must be reliable; its storage must be durable; and its success must be verifiable. CDR must also be additional: it must cause more carbon to be removed from the atmosphere than if it had not been implemented, and its impacts must be measured on a net basis, including upstream and downstream emissions. Finally, it must be a net benefit for human and nonhuman life on Earth, meaning that its negative environmental and social impacts must be substantially exceeded by its benefits (Jeswani, Saharudin, & Azapagic, 2022). The question of how to value environmental impacts is beyond the scope of this roadmap, but is a crucial question for humanity to reckon with as we extend our agency into the realm of geoengineering, particularly given our history of destroying ecosystems in favor of industry and perceived human benefit. For a more nuanced discussion of the criteria for quality CDR, see (Allen et al., 2020; Carbon Direct, 2023).
Many CDR pathways3 are under development, with the goal of meeting the five essential criteria. The CDR Primer by Wilcox et al., 2021 gives a concise introduction to many CDR pathways, and (Minx et al., 2018) offers a more detailed review. Two recent reports by the National Academies of Sciences, Engineering, and Medicine (NASEM) provide extensive overviews and discussions of technology needs (NASEM, 2019)(NASEM, 2022).
We stress that a CDR “pathway” refers to the full process of carbon being removed from the atmosphere and transferred into storage. We should collectively avoid referring to a process as “carbon removal” without having in mind a full pathway from the separation of CO2 from air to durable storage. For example, improvements to photosynthesis cannot be evaluated as CDR unless there is a clear additive pathway from fixed carbon to durable storage, because photosynthetically-fixed carbon is typically returned to the atmosphere by some means.
CDR methods fall roughly into four categories, with some overlap:
Direct air capture (DAC) methods process ambient air in industrial facilities to separate the CO2(Erans et al., 2022) typically producing high-purity CO2 (>95%) that is ready for storage. DAC is reviewed thoroughly by (Erans et al., 2022), and many publications on DAC can be found in the DAC Coalition’s Report Library.
Geochemical CDR methods neutralize CO2, an acid, with mineral-derived alkalinity and convert the CO2 to either (bi)carbonate ions dissolved in water or solid carbonates. Geochemical methods can be used for separating CO2 from air or for durable storage of concentrated CO2 downstream of other methods, such as DAC. Campbell et al.(Campbell et al., 2022) and (Sandalow et al., 2021) provide reviews.
Biomass carbon removal and storage (BiCRS) methods take up carbon from air into biomass via photosynthesis and then transfer it to durable storage. Biomass may be thermochemically converted to concentrated CO2, biochar, or bio-oil before storage, or it may be stored in its native form in an environment that inhibits degradation. BiRCS is reviewed in (Sandalow et al., 2021).
“Nature-based” or “natural climate solution” methods seek to store carbon in ecosystems, soils, and sediments through conservation, land/ocean management or agriculture.
This roadmap focuses on opportunities for biotechnology to contribute to the first three categories. As discussed below under “Scope,” we did not focus on the fourth category, but we acknowledge that many methods in that category merit pursuit.
The technical body of the roadmap provides details regarding various CDR pathways and their underlying mechanisms, as pertains to the opportunities for biotechnology to contribute to CDR.
Brief introduction to biotechnology
Organisms’ multiple existing roles in the carbon cycle, including photosynthesis, biomass, and their interactions with minerals, suggest strong potential for applying biology to CDR technology. Organisms have evolved to survive in diverse contexts by adaptively manipulating energy, minerals, and organic compounds to construct their bodies and extract resources from their environment. They are composed of functional biomolecules4 that enable atomically-precise manipulation of materials via a wide range of chemical mechanisms and properties.
Biotechnology—methods and applications of measuring, manipulating and synthesizing biomolecules for human purposes—has profoundly impacted biomedicine, agriculture, and manufacturing. It has grown rapidly over recent decades and continues to be among the fastest-growing technological domains. Progress has been driven by synergistic advances in hard technologies (e.g., DNA sequencing and synthesis), biological data science, and utilization of naturally-evolved biological functions discovered using the tools of biotechnology itself. An illustrative example of the pace of progress in biotechnology is the development of DNA sequencing, for which the pace of cost reduction has matched or exceeded Moore's law5 since the 1980s (Shendure et al., 2017)(Pennisi, 2022).6
Technologies for measuring and modifying biological systems have developed notable emerging capabilities in multiple domains.
BOX. Measurement biotechnologies
Protein structure measurement and prediction aids mechanistic understanding and engineering biological processes involving proteins. Proteins are the most common catalysts and molecular binders in biology. In particular, cryogenic electron microscopy (cryo-EM) substantially simplifies the workflow of empirical structural determination (Danev, Yanagisawa, & Kikkawa, 2019), and machine learning can predict protein structure with high accuracy based on existing measurements (largely supplied by cryo-EM) (AlQuraishi, 2021).
Nucleic acid sequencing provides information on an organism’s genetic information (DNA) and gene expression (RNA). In addition to rapid cost-reduction, novel long-read nucleic sequencing technologies provide improved detail on sequence variants and facilitate genomic studies on organisms with highly-redundant genomes (Wang, et al., 2021), including many plants (Jung et al., 2019). Single-cell RNA sequencing provides information about gene expression of single cells (Kolodziejczyk et al., 2015), including bacteria (Ma et al., 2023). Also, sequencing-based assays have been developed to obliquely measure many other biological features, including epigenetic states (Klemm et al., 2019)(Zhao et. al, 2020) and the specific interactions of proteins with DNA (Furey, 2012).
Metagenomics and metatranscriptomics measure the microbial species present in a microbial community and their gene expression (Laudadio et al., 2019)(Zhang et al., 2021). These measurements allow insight into the metabolic mechanisms by which microbial communities function and the roles of distinct microbial species.
Spatially-resolved omics combines imaging and sequencing technologies to provide data on the spatial organization of biomolecules within cells, organisms, and microbial communities (He et al., 2022). In contrast, traditional “omics” approaches (such as genomics and proteomics) study biomolecules in the absence of spatial features, losing key functional features arising from structure.
BOX. Modification biotechnologies
Protein engineering enables design of proteins with desired functions, either through directed evolution, rational design, or increasingly powerful machine learning tools for modifying existing proteins and de novo protein design (Wang et al., 2021)(Meinen & Bahl, 2021)(Lovelock et al., 2022). For example, protein engineering can enable catalysis of biochemical reactions; gene regulation in response to sensing a specific molecule or ion; and stability in novel environmental conditions, among many other applications.
Metabolic engineering enables modification of organisms to produce or degrade desired chemical compounds using metabolic engineering, including many-enzyme (e.g., >10 enzymes) metabolic pathways (Choi et al., 2019).
Genome engineering enables modification of organismal DNA by inserting synthetic DNA, modifying sequences at specific locations, or even synthesizing much or all of a genome (Pickar-Oliver & Gersbach, 2019)(Gao, 2021)(Venter et al., 2022). CRISPR technology is a prominent example. Genome engineering can enable changing an organism's morphology, such as root or leaf size; conferring novel traits, such as metabolizing specific chemicals or tolerating novel environmental conditions; or even altering the genetic code of an organism so that it can use novel amino acids in its proteins, among a diversity of other applications.
These and other advances continue to increase our capability to study new biological systems, reveal mechanisms for making biological interventions, and develop technology for new applications. Simultaneously, parallel advances in automation and machine learning are also increasing the throughput and complexity of what can be achieved using biotechnology.
Most of these foundational advances in biotechnology have been developed for biomedical applications, as a result of substantial funding.7 However, we anticipate that 21st century biotechnology will be marked by growth of applications in climate and sustainability, such as CDR, alongside biomedicine. In addition to continued technological development, progress will include developing biological understanding of a greater diversity of organisms with practical utility8 and tools for their genetic manipulation. By highlighting opportunities for research and funding, we intend for this roadmap to help accelerate and expand the development of biotechnology for CDR.
Scope
Early ideas for bringing biotechnology tools to bear on CDR have emphasized biogeoengineering, in which genetic tools are used to augment nature-based solutions by modifying organisms to take up and store carbon within the context of ecosystems.9 Examples include various notions for engineering phytoplankton to fix more carbon (Y Combinator 2020) and the Salk Institute's Harnessing Plants Initiative which seeks to produce suberin, a slow-degrading biopolymer, in the roots of plants to be stored in soil. These avenues of research may yield important results.
However, we focus on a less-explored direction: using biotechnology in “engineering-based” methods and open-system methods for which CDR and storage mechanisms rely minimally on modifying or predicting ecosystems’ behaviors . Where we do consider CDR–ecosystem interfaces, we prioritize opportunities for biotechnology to reduce uncertainty by contributing to science and measurement for assessing the durability and impact of CDR. This focus also allows us to prioritize CDR that is durable over the long-term (>>100 years).
We propose that methods with the least reliance on ecosystems offer the greatest reliability, because ecological dynamics are relatively difficult to predict compared to the dynamics of abiotic or engineered processes, particularly under large-scale perturbations from CDR mechanisms. Due to that low predictability, we anticipate that the principal technical challenges and scientific unknowns of methods involving ecosystem dynamics rather than engineering or abiotic processes will involve a categorically different and more challenging type of uncertainty regarding the mechanisms and durability, as well as the environmental impacts, of CDR. Moreover, the sensitivity of some ecosystem dynamics to the effects of climate change itself, such as mean temperature rise, altered weather patterns, and extreme weather, may compound such uncertainty (Seddon et al., 2020)(Bradford et al., 2016).
Nonetheless, many nature-based solutions are promising for reducing atmospheric CO2 and also offer environmental benefits (such as reforestation and increased soil carbon). It would be valuable to conduct a similar study focused on identifying opportunities for biotechnology to impact nature-based solutions, with a special focus on ways that biological measurement technologies can be used in scientific studies to reduce uncertainty regarding the mechanisms and durability of CDR.
Methods and structure
To identify opportunities for biotechnology in CDR, we sought instances where biotechnology can substantially impact the constraints on leading CDR pathways that are already under serious consideration (a “bottom-up” approach), rather than attempting to identify the most promising overall CDR pathways using biotechnology (a “top-down” approach).
We define constraints as aspects of proposed technology, current technology, and current knowledge that limit either the estimated utility of a CDR pathway or our ability to estimate that utility. We specifically consider constraints in three categories:
Cost constraints, processes and components involved in a technology that contribute most to cost;
Scaling constraints, resource needs that prevent deployment at large scale, irrespective of cost; and
Environmental constraints, ecological impacts resulting from use of the technology at large scale.10
We do not consider constraints related to market, policy or regulatory factors, which are largely external to the engineering domain. For example, regulatory restrictions on the use of genetically modified organisms (GMO) may complicate efforts to deploy CDR technology that incorporates genetically-modified components, but we do not attempt to assess or incorporate that issue here.
This roadmap is composed of three technical parts (Parts 1, 2, and 3), published serially, in addition to this introduction. The technical parts deal with methods that are grouped together due to similarities among their constraints and conceptual bases. They focus on 1) solvent-based CO2 capture, such as some forms of direct air capture (DAC); 2) geochemical methods for CDR, such as enhanced mineral weathering; and 3) methods for biomass-based carbon removal and storage (BiCRS) that rely minimally on ecosystem dynamics, such as controlled cultivation of biomass for input to bioenergy carbon capture and storage (BECCS).
Each of the three technology-focused parts follows the same structure. We begin with an overview of the pathways for CDR under consideration, followed by a non-exhaustive description of the constraints that limit each pathway. Rather than listing all constraints, we have chosen to describe only those we find may be addressable by biotechnology, because an exhaustive analysis of the constraints on CDR is outside the scope of this roadmap.11 We then present a series of conceptual solutions by which biotechnology may alleviate those constraints and discuss the expected challenges and possible solution pathways for each. The ideas are presented roughly in order of priority. At the end of each part, we give a list of actionable recommendations for pursuing the solutions discussed.
How to engage with this roadmap
Each of the four primary audiences for this roadmap will find it useful in different ways.
Audience
Recommended approach to this roadmap
Biotechnology practitioners (academia and industry)
The background information12 and description of constraints on CDR technology given at the beginning of each technical part are intended to frame problems in CDR that are addressable by biotechnology.
The list of possible solutions given in each technical part provides actionable project ideas. These provide conceptual descriptions of ways biotechnology addresses constraints on CDR and expected challenges.
The list of recommendations at the end of each technical part is useful for identifying priority research directions that relate to individual or institutional skillsets.
CDR technology practitioners (academia and industry)
May already be familiar with the introductory content and framing of problems given at the beginning of each of the technical parts of the roadmap.
The list of possible solutions given in each technical part will have great utility because it describes ways that biotechnology can impact current and future work in CDR.
The list of recommendations at the end of each technical part identifies the ways that biotechnology can contribute to problems relevant to current work.
People constructing research programs/agendas;
research funders and investors
The list of possible solutions given in each technical part shows avenues for program development: each possible solution typically requires a set of mutually supportive research projects to which effort and funding can be directed.
The list of recommendations at the end of each technical part identifies specific research directions that relate to relevant programming domains.
Biotechnology program managers and funders
See the list of possible solutions and list of recommendations as described for the audience immediately above.
The background information and description of constraints on CDR technology given at the beginning of each technical part provide additional clarity regarding the applications and problems in CDR that the proposed solutions are intended to address.
Recommendations
Develop multidisciplinary opportunities. The CDR and biotechnology communities should be more integrated. University educational curricula, research initiatives, consortia, and funding in biotechnology and CDR should be intentionally designed as interdisciplinary efforts. Large competitive grants should be made available to support the multidisciplinary teams that are required to effectively pursue many of the research challenges we describe in the technical body of this roadmap.
Compile knowledge of constraints. To convey high-priority problems to researchers in disciplines outside CDR who want to apply their skills to high-impact problems, a knowledge resource focused on explaining the technical constraints on CDR pathways should be assembled. This could resemble Frontier's Carbon Removal Knowledge Gaps Database, but would provide a deeper characterization of each constraint and contextualize them relative to each other. Such a resource would be valuable for efforts similar to this roadmap that seek opportunities for existing disciplinary communities.
Interrogate opportunities with nature-based solutions. A similar study to this roadmap should be pursued that focuses on opportunities for biotechnology to contribute to nature-based solutions. Like this one, it should lead with constraints on each pathway and identify opportunities to address those constraints.
Build cross-disciplinary libraries. A knowledge resource should be assembled that introduces the tools of biotechnology to CDR technologists as a resource to enable cross-disciplinary understanding.
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