By Brad Warren, NFCC\/Global Ocean Health, Revised December 1st, 2019<\/p>\n\n\n\n
For decades, failure to reduce carbon\npollution has been a central conundrum for humankind, producing obvious consequences\nacross both marine and terrestrial systems. Unchecked carbon emissions are\ndegrading marine foodwebs, disrupting fisheries production, threatening world\nseafood supplies, and propelling many other troubling changes.<\/p>\n\n\n\n
Despite earnest and intelligent\nefforts, greenhouse gas emissions have increased by 55% since 1990 (Olivier\n& Peters 2018). The dominant component of this swelling emission stream is\ncarbon dioxide (73% of the total), almost entirely from burning fossil fuels.\nIn many developed nations, carbon emissions have continued to increase in the\ntransportation sector even as other sectors of the economy have managed to\nflatten or reduce emissions. Over the last five years, monthly mean atmospheric\nconcentration of CO2<\/sub> (recorded at Mauna Loa Observatory) has climbed\nfrom about 398 ppm to 410 ppm (NOAA 2018).<\/p>\n\n\n\n In response to this conundrum, some\nleaders in business, government and the scientific community developed new ways\nto reduce pollution that may be achievable without a major fight with fossil\nfuel interests ,which have successfully blocked most other pathways. A major\nclass of intervention that is generating increased attention lately (and\nattracting some investment from oil companies) is carbon removal. The enabling\ntools are sometimes described as Negative Emissions Technologies (NETs).\n<\/strong>Drawing down CO2<\/sub> to help mitigate changes in climate and\nsometimes ocean chemistry, these approaches harness natural systems (both\nterrestrial and marine) and abiotic technologies (carbon capture and\nsequestration systems). <\/p>\n\n\n\n These technologies have important\nimplications for the future of marine resources and ocean use. Any plausible\npathway to large-scale emissions removal requires a place to put the carbon,\npotentially on a scale of tens of billions of tons annually. The signs point to\nthe ocean. The ocean and coastal zones are primary venues for many\nsequestration projects, in part due to the geochemistry of saline aquifers\nwhich facilitates reactions that bind carbon into carbonate minerals. As carbon\ndioxide removal grows into a major industry, we anticipate a need to learn\nquickly how to govern it, how to structure enterprises for optimal performance\nand public accountability, and how to refine the technologies to ensure that\nrisks are well contained. <\/p>\n\n\n\n Negative Emissions Technologies<\/strong><\/strong><\/p>\n\n\n\n Options to accelerate capture and\nsequestration of CO2<\/sub> in natural and artificial systems have become\nan important theme in global climate policy discussions. They provide a supplemental\nstrategy at a time when leaders and researchers anticipate that climate targets\ncannot be achieved through emission reduction alone. Indeed, negative emissions\ntechnologies (NETS) play a part in most emissions scenarios that could limit\nglobal warming to 2\u00b0C in the latest IPCC Assessment Report (2014) according to\na review of NETS options and their limitations published in Nature<\/em> (Smith et al 2016).<\/p>\n\n\n\n Authors of a 2018 US National\nAcademies of Science, Engineering and Medicine study on NETs noted: \u201cit would\nbe extremely difficult to reduce net anthropogenic emissions enough to achieve\ndeclining atmospheric CO2<\/sub> without the use of NETs because of fossil\nand land-use sources that would be extremely disruptive or expensive to\nmitigate, such as some agricultural methane or CO2<\/sub> from air travel.\u201d\n(National Academies 2018). The National Academies study authors observe that\nNETs offer the most powerful known mechanisms to reduce atmospheric\nconcentration of GHGs: \u201cUnlike other forms of mitigation, NETs provide the only\nmeans to achieve deep (i.e. > 100 ppm) emissions reductions, beyond the\ncapacity of the natural sinks.\u201d<\/p>\n\n\n\n Several approaches to CO2 <\/sub>drawdown may deliver additional benefits that serve or complement conservation priorities:\u00a0 earning revenue, creating jobs, conserving and restoring habitats, and locally remediating ocean acidification and other pollution that degrades habitat and water quality. <\/p>\n\n\n\n Natural systems offer low-cost\ndrawdown<\/strong>. Compared to artificial methods, the\nNational Academies study found that drawdown approaches using natural systems\noffer significant cost advantages, but vary widely in their potential to remove\nlarge quantities of CO2<\/sub> from circulation (see Table 8.1 from\nNational Academies report, reproduced on page 11). The study evaluated coastal\nblue carbon, forest carbon, agricultural soil carbon, biofuel energy production\nwith carbon capture and sequestration, direct air capture, and four variants of\nmineralization, an approach that captures carbon and binds it in mineral form.\nNarrowing this list, the report identifies four land-based NET approaches \u201cthat\ncould be scaled up to capture and store substantial amounts of carbon.\u201d It\nshould be noted that other authors in the field see additional opportunities\nfor removing emissions at larger scale in the ocean. Those will be addressed\nbelow. The four approaches identified by the National Academies authors are\nafforestation\/reforestation, changes in forest management, uptake and storage\nby agricultural soils, and biomass energy with carbon capture and storage\n(BECCS). <\/p>\n\n\n\n The NAS authors observe: \u201cThese\napproaches have co-benefits, including:<\/p>\n\n\n\n Forest carbon<\/strong>. To date, forest carbon is the most fully developed form\nof NET. The National Academies study estimates the worldwide potential of this\napproach to be large: between 570 and 1125 GT of CO2, <\/sub>removal, at\ncosts of $15 to $50 per ton removed. \nHowever, the study estimates that the total removal potential for\nforests in the US is modest, with a range of 0.15 to 38 GT.<\/p>\n\n\n\n Increasing carbon storage in\nagricultural soils is another large, low-cost option. Estimated costs per ton\nof CO2 <\/sub>run $0-50 for climate-friendly agricultural practices that\nenhance soil sequestration (In some cases, soil-based carbon sequestration may\ncarry no cost because farmers can profitably switch to soil-regenerating,\ncarbon-burying practices)<\/p>\n\n\n\n One potentially important pathway for\nmineralization of CO2 <\/sub>is called \u201caccelerated weathering\u201d because it\ninvolves speeding up the natural process by which alkaline rocks gradually\nweather into rock powder, mix into water and bind CO2 <\/sub>over geologic\ntime. The Academies authors estimate the cost per ton of CO2 <\/sub>removed\nthrough such processes to be as low as <$10 for the least-cost options of\nthis type. <\/p>\n\n\n\n Coastal blue carbon is characterized\nas a small but low-cost option. The National Academies study reports that blue\ncarbon could remove an estimated 0.26 to 4 GT of CO2<\/sub> in the US and 8\nto 65 GT worldwide, at a cost of $10\/t.<\/p>\n\n\n\n How far can it go?<\/strong> The volume of CO2 <\/sub>that can be removed by NET\napproaches is still subject to debate. However, the NAS report also notes that\nmany constraints will narrow the scope for NET deployment. Focusing on\nopportunities that could be achieved safely and at costs below $100\/t, the\nNational Academies study reckons that the four land-based technologies\nidentified as ready to scale up (see detail above) potentially could remove up\nto 1 GT of CO2<\/sub>\/yr in the US, and up to 10 GT\/yr globally. <\/p>\n\n\n\n The authors note that practical\nconstraints are likely to prevent the four land-based approaches from attaining\ntheir maximum potential. Further, they concur with other authors (Rau et al\n2018) in concluding that even those ambitious levels for land-based CO2 <\/sub>removal\nwill fall short. They observe that \u201cattaining these levels (e.g. up to 1 GT\/yr\nremoval in the US, and 10 GT\/yr globally) would require unprecedented rates of\nadoption of agricultural soil conservation practices, forestry management\npractices, and waste biomass capture.\u201d <\/p>\n\n\n\n At the same time, the world will need\nmore, larger tools to draw down CO2<\/sub> (even presuming that efforts to\ncut emissions are successful), if we aim to stabilize the climate at <2\u00b0C of\nwarming. The National Academies authors estimate that \u201cNETs will likely need to\nramp up rapidly before mid-century to remove up to 20 GT CO2<\/sub>\/yr\nglobally by century\u2019s end.\u201d<\/p>\n\n\n\n Other investigators support views\noffered by the National Academies authors on several key points: <\/p>\n\n\n\n In a study evaluating the limits to\ndrawdown technologies, Smith et al (2016) also offer the reservation that some\nNETs, especially the important category of bio-energy combined with carbon\ncapture and sequestration (BECCS) will face competition for land, water and\navailable nutrients. <\/p>\n\n\n\n Smith et al also warn that reliance on\nNETs \u201cto allow continued use of fossil fuels in the present is extremely risky\u201d\ndue to uncertainties about the biophysical and economic limits that could\nprevent these tools from scaling up enough to stabilize the climate. Smith and co-authors observe that \u201cthere is\nno NET, or combination of NETs, available now that could be implemented to meet\nthe <2\u00b0C target without significant impact on either land, energy, water,\nnutrient, albedo or cost.\u201d Smith and co-authors conclude: \u201c\u2019Plan A\u2019 must be to\nreduce GHG emissions aggressively now.\u201d <\/p>\n\n\n\n The IPCC emphatically concurs with\nthis warning. Its draft 2018 Special Report (IPCC 2018) focuses on ways to\navoid crossing the tighter threshold for warming that has emerged from recent\nresearch: a limit of 1.5\u00b0C. That ambitious new target demands deeper cuts in\nemissions and could push nations to lean harder on carbon dioxideremoval\n(CDR). But the IPCC warns against over-dependence on such a novel, untested\napproach: \u201cCDR deployed at scale is unproven and reliance on such technology is\na major risk in the ability to limit warning to 1.5\u00b0C.\u201d The\npanel affirms the view that land-based CDR via forest or BECCS will face \u201ctrade-offs\nwith other sustainability objectives\u2026 predominantly through increased land,\nenergy, water and investment demand.\u201d<\/p>\n\n\n\n For better or worse, the world now is\ncommitted to CO2 <\/sub>drawdown, whatever its risks. There is no way to\navoid long-lasting commitment to warming above 1.5\u00b0C without it. As the IPCC\n2018 draft Special Report authors note: \u201cAll analyzed 1.5\u00b0C \u2013consistent\npathways use CDR to some extent to neutralize emissions from sources for which\nno mitigation measures have been identified and, in most cases, also to achieve\nnet-negative emissions that allow temperature to return to 1.5\u00b0C following an\novershoot (high confidence<\/em>). The longer the delay in reducing CO2 <\/sub>emissions\ntoward zero, the larger the likelihood of exceeding 1.5\u00b0C, and the heavier the\nimplied reliance on net-negative emissions after mid-century to return warming\nto 1.5\u00b0C.\u201d <\/p>\n\n\n\n Going to sea.<\/strong> The world\u2019s increasing, if inadvertent, commitment to\nlarge-scale CDR heightens the need for research on the biggest potential venue\nfor CO2<\/sub> removal: the ocean. Greg Rau, a marine chemist and\nresearcher at UC Santa Cruz, is one of the pioneers of methods for accelerating\nCO2<\/sub> removal in the ocean. Rau has advocated an increase in scientific\nresearch to better understand the potential and limitations of the ocean\u2019s\ncapacity to clean up humankind\u2019s biggest pollution problem. Rau notes that the\nocean covers 70% of the Earth, provides more than 90% of its existing surface\nstorage of carbon, and performs 50% of natural CO2<\/sub> removal today\n(Rau pers. comm. 2, 2018) by absorbing the gas from the air and capturing it in\nbiological and geological forms. It should noted that experts on CDR are still\ndebating the relative importance of land-based and marine carbon transfer.\nAuthors of the 2018 NAS report took a more conservative view of ocean carbon\nsinks, which they estimated to be\nsmaller than terrestrial ones. The NAS authors focused mainly on terrestrial approaches,\nand considered marine CDR potential only from \u201ccoastal blue carbon,\u201d the narrow\nstrip of photosynthesizing marine grasses and algae that occupies estuaries and\nshores. <\/p>\n\n\n\n Rau and co-authors (Rau et al 2018)\nfound that one suite of marine-based technologies could yield 50 times more CO2\n<\/sub>reduction and energy than BECCS, at lower cost. Their study examines the\nmagnitude and feasibility of technologies to amplify the CO2 <\/sub>reduction\npower of some NETs by converting electricity (from bio-fuels, wind and solar\nsources) to negative-emissions hydrogen. This approach uses electrolysis to\nextract hydrogen from water.<\/p>\n\n\n\n Referred to as \u201cnegative-emissions\nhydrogen\u201d (NE H2<\/sub>) this approach may hold particular interest for\nfishery-dependent coastal communities, states, and enterprises, for several\nreasons: <\/p>\n\n\n\n Rau notes that this electrochemical\napproach could be piloted at small scale in bays to assess potential use of\ncarbonate mineral byproducts to remediate acidification. (Rau pers. comm. 2018). If successful, this could add a new tool to the kit for\naddressing the increasingly severe acidification impacts noted in 2017 by\nWashington\u2019s Marine Resource Advisory Council, which carries forward the work\nof the state\u2019s original Blue Ribbon Panel on Ocean Acidification. The Advisory Council noted (Washington MRAC\n2017) that acidification is now affecting both wild and cultured bivalves in\nthe region and causing visible damage to planktonic species (notably pteropods)\nthat form an important part of salmon diets.<\/p>\n\n\n\n The Renewable Hydrogen\nAlliance<\/a>,\nbased in Portland Oregon, is a new forum established by leaders in renewable\nenergy and utilities to pursue a vision that could complement the potential of\nsome NETs approaches both on land and at sea. They envision using electrolysis\npowered by ultra-low-cost renewable power at times of surplus solar and wind\nproduction. Converting this electricity to hydrogen ensures the cheap power can\nbe used (not wasted) when needed. This makes \u201ca more efficient use of the\nenergy created and increases the value of renewables by creating flexible\ndemand for power when it can\u2019t otherwise be efficiently put to good use.\u201d This\nrenewably produced hydrogen, in time, could gradually replace hydrogen derived\nfrom natural gas, with its significant carbon footprint. \u201cTransitioning to\ncreating hydrogen from water and renewable electricity is a vital part of\nrealizing a low-carbon future,\u201d the group states.<\/p>\n\n\n\n Seaweed-based solutions. <\/strong>Another approach that may be consistent with conservation\npriorities is growing marine macroalgae to reduce CO2<\/sub>concentration\nin seawater, remediating local acidification and potentially contributing to\nglobal emissions reduction and adaptation approaches. A major review of seaweed potential in\nclimate solutions (Duarte et al 2017) identified multiple benefits to this\napproach. Seaweed farms export carbon as detritus to marine sediments, where it\nis thought that currents can carry it to the deep sea for long-term\nsequestration. Production of biofuel from seaweed crops can yield CO2 <\/sub>mitigation\nof ~1,500 tons CO2 <\/sub>per km-2 <\/sup>(i.e. 1\/4 of square\nkilometer). Duarte and co-authors observe: \u201cSeaweed aquaculture can also help\nreduce the emissions from agriculture, by improving soil quality substituting\nsynthetic fertilizer and when included in cattle feed, lowering methane\nemissions from cattle.\u201d This form of aquaculture also enhances coastal climate\nresilience by \u201cdamping wave energy and protecting shorelines, and by elevating\npH and supplying oxygen to the waters, thereby locally reducing the effects of\nocean acidification and de-oxygenation.\u201d<\/p>\n\n\n\n Duarte and co-authors estimate the\nupper limit for CO2 <\/sub>capture by cultured seaweed worldwide at about\n2.48 million tons annually, assuming that all of the 27.3 million tons fresh\nweight produced in 2014 could be dedicated to carbon capture. They note,\nhowever, that \u201cthis upper limit constitutes only about 0.4% of the global wild\nseaweed CO2 <\/sub>capture\u201d over an area of 3.5 million km2<\/sup>.\nDuarte et al conclude that seaweed aquaculture, covering only about 1,600 km2<\/sup>\ntoday, \u201cdoes not yet have a scale that would support a global role in climate\nchange mitigation,\u201d but its intensity of 1,500 tons CO2 <\/sub>per km-2\n<\/sup>could be a significant tool for local climate strategies. Acknowledging\nthat marine nutrient supplies, light availability and other factors may\nconstrain expansion of seaweed crops, Duarte et al still find that \u201cthe scope\nfor expansion of seaweed aquaculture with available structures and constraints\nis substantial.\u201d They note that Norway has identified seaweed aquaculture as a\npromising field for expansion, tripling the area under cultivation along its\ncoast from 2014 to 2016. <\/p>\n\n\n\n While Duarte et al find that seaweed\nfarming \u201ccannot be the option of choice if the sole intent is to mitigate\nclimate change,\u201d they note that it provides a lower-cost option than offshore\nwind power development. A 1-hectare seaweed farm can be started with an initial\ninvestment of $15,000 in Mexico, \u201cwhereas a state-of-the-art offshore wind\nturbine, including installation, is about $1.5 million per turbine, and\ninvolves order-of-magnitude larger maintenance costs.\u201d Duarte and co-authors\nsuggest that this cost advantage, coupled with co-benefits from food, biomass,\nanimal feed, and other functions, could make seaweed farming a suitable option\nfor developing countries that cannot afford more expensive solutions.<\/p>\n\n\n\n From Waste to Resource: <\/strong>Environmental engineering technologies are increasingly\ncapable of capturing carbon and other materials from wastewater\nand converting it to beneficial uses. This applies to both municipal and\nindustrial wastewater, with potential to deliver multiple co-benefits. In\naddition to their massive discharges of nutrient wastes, wastewater treatment\nplants generate about 1.6% of the world\u2019s greenhouse gas emissions, and consume\nnearly 3% of global electricity. Indeed, \u201cfor many cities and towns, wastewater\ntreatment plants are the largest energy consumers,\u201d note Lulu et al (2018) in a\nnew paper published in Nature Sustainability <\/em>that proposes to capture\nand reuse carbon emissions and other wastes from these processes. <\/p>\n\n\n\n A combination of electrochemical,\nmicrobial, and phototrophic processes can reduce emissions and water pollution,\nprovide materials for habitat restoration and soil-building farming practices,\nLulu and co-authors report. Their paper offers a broad range of technical\napproaches, many of which show potential to serve tribal priorities for\nenvironmental cleanup and restoration as well as emission reduction. Lulu and\nco-authors propose that wastewater treatment can be integrated with carbon\ncapture and utilization (CCU) and other technologies to perform a more useful\nfunction as \u201cwater resource recovery facilities\u201d (WRRFs). These could \u201crecover\nenergy, nutrients, water and other valuable carbon products with economic,\nenvironmental and social benefits.\u201d<\/p>\n\n\n\n In one example, Lulu and coauthors\ndescribe how electrolytic carbon capture can be applied, using wastewater as\nthe electrolyte in a microbially-assisted process. This approach can extract\n80-93% of CO2<\/sub>and 50-100% of organics from wastewater. It\nalso generate a net energy gain\u2014potentially turning wastewater treatment plants\ninto power plants.<\/p>\n\n\n\n The authors note that use of\nconstructed wetlands can accelerate capture of CO2<\/sub>, while other\nmethods have been demonstrated to simultaneously capture and utilize CO2<\/sub>\nfrom wastewater while removing nutrient wastes that normally are discharged to\ndownstream waters. <\/p>\n\n\n\n One interesting approach suggested by\nthese authors is the conversion of wastewater sludge to biochar. Lulu and\nco-authors note that this carbon-rich material can substitute for woody biomass\nas a feedstock for production of biochar for use in soil enrichment and\nremediation of pollutants and environmental hazards. They write: \u201cCompared with\ncurrent disposal practices of landfilling and direct land application,\ncarbonizing the sludge into biochar may provide higher environmental and\neconomic benefits. Sludge biochar eliminates pathogens, improves soil structure\nand increases agricultural output. Moreover, studies have shown that such\nbiochar can adsorb pesticides, reduce heavy metal leaching and increase soil\nfertility.\u201d They cite research indicating sharp increases in yield for cherry\ntomatoes grown in soil enriched with sludge biochar. <\/p>\n\n\n\n Incorporation of biochar into soils\nalso sequesters carbon. Citing previously published research on this approach.\nLulu and co-authors calculate as follows: \u201cFor a wastewater treatment plant\ngenerating 100 dry tons of sewage sludge per day, an estimated 65 tons of\nbiochar can be generated assuming a median yield of 65% and ~21 ktCO2<\/sub>e\nmay be captured per year based on a GHG emission of 0.9 kg CO2<\/sub>e per kg biochar.\u201d<\/p>\n\n\n\n By converting industrial wastewater\ninto a resource instead of a waste product, Lulu and co-authors note that substantial\namounts of GHG reduction and other environmental benefits can be realized. They\nwrite that \u201cnearly 3.3 billion cubic meters of wastewater are generated from\nthe oil and gas industry ever year in the US alone. The use of such waste\nstreams for in situ CCU of GHGs from oil and gas could have significant\nbenefits for the industry, not the least of which would stem from environmental\nand economic benefits of water reuse relative to deep well injections.\u201d <\/p>\n\n\n\n Key Take-home Points<\/strong><\/strong><\/p>\n\n\n\n Additional figures and tables\nbelow:<\/strong><\/p>\n\n\n\n F<\/strong><\/p>\n\n\n\n REFERENCES<\/strong><\/strong><\/p>\n\n\n\n Duarte et al 2017. Can Seaweed Farming Playa Role in\nClimate Change Mitigation and Adaptation? Frontiers in Marine Science, 12 April\n2017, https:\/\/www.frontiersin.org\/articles\/10.3389\/fmars.2017.00100\/full<\/a>\n<\/p>\n\n\n\n EIA 2016. Primary energy, electricity, and total energy\nexpenditure estimates, 2016.\u201d Energy Information Administration. https:\/\/www.eia.gov\/state\/seds\/seds-data-complete.php?sid=WA#PricesExpenditures<\/a><\/p>\n\n\n\n Hibbard et al 2018. The Economic Impacts of the Regional\nGreenhouse Gas Initiative on Nine Northeast and Mid-Atlantic States. Analysis Group, April 17, 2018. https:\/\/www.analysisgroup.com\/globalassets\/uploadedfiles\/content\/insights\/publishing\/analysis_group_rggi_report_april_2018.pdf<\/a><\/p>\n\n\n\n IPCC 2014. Climate Change 2014: Mitigation of Climate Change. Working Group III Contribution to the Fifth Assessment Report, Intergovernmental Panel on Climate Change, 2014. Edenhofer et al, eds. https:\/\/www.ipcc.ch\/site\/assets\/uploads\/2018\/02\/ipcc_wg3_ar5_full.pdf<\/a>h<\/a><\/p>\n\n\n\n IPCC 2018. Special\nReport: Global Warming of 1.5o <\/sup>C, Technical Summary,\nIntergovernmental Panel on Climate Change, 2018. https:\/\/www.ipcc.ch\/sr15\/about\/<\/a><\/p>\n\n\n\n Lulu et al 2018. Wastewater treatment for carbon capture and utilization. Nature Sustainability, Vol 1, December 2018,\u00a0 750-758. https:\/\/www.nature.com\/articles\/s41893-018-0187-9.epdf?author_access_token=jE1cDdPhW80MEB4P0Yp-7dRgN0jAjWel9jnR3ZoTv0MI9dfBew-n2U3AxOPRibsgS5pyl0Ei5ZESPB73SpLIqmsVp9ndk2gprkHwwGb2KuQAwQBcSxh0fGGwnWFGBRCLST9tLkBuUL3W-MS-m7kvpQ%3D%3D<\/a>h<\/a><\/p>\n\n\n\n Murray et al 2015. An inland sea high nitrate-low\nchlorophyll (HNCL) region with naturally high pCO2<\/sub>, Limnology and\nOceanography, 60, 2015, 957-966. https:\/\/aslopubs.onlinelibrary.wiley.com\/doi\/pdf\/10.1002\/lno.10062<\/a><\/p>\n\n\n\n National Academies 2018. Negative Emissions Technologies\nand Reliable Sequestration: A Research Agenda. National Academies Press. https:\/\/doi.org\/10.17226\/25259<\/a>, also: https:\/\/www.nap.edu\/catalog\/25259\/negative-emissions-technologies-and-reliable-sequestration-a-research-agenda<\/a><\/p>\n\n\n\n NOAA 2018. Recent Monthly Mean Average Mona Loa CO2\u00a0 <\/sub>Earth System Research Laboratory,\u00a0 Global Monitoring Division, National Oceanic & Atmospheric Administration. https:\/\/www.esrl.noaa.gov\/gmd\/ccgg\/trends\/index.html<\/a><\/p>\n\n\n\n Olivier & Peters, 2018. Trends in Global CO2 <\/sub>\u00a0and Total Greenhouse Gas Emissions: 2018 Report, PBL Netherlands Environmental Assessment Agency, December 2018. https:\/\/www.pbl.nl\/sites\/default\/files\/cms\/publicaties\/pbl-2018-trends-in-global-co2-and-total-greenhouse-gas-emissons-2018-report_3125.pdf<\/a><\/p>\n\n\n\n Pacella et al 2017. Seagrass habitat metabolism increases\nshort-term extremes and long-term offset of CO2<\/sub> under future ocean\nacidification. Proceedings of the National Academy of Sciences (PNAS), published ahead of print April 2,\n2018. https:\/\/doi.org\/10.1073\/pnas.1703445115<\/a><\/p>\n\n\n\n Rau et al 2018. The global potential for converting renewable\nelectricity to negative- CO2<\/sub>-emissions hydrogen. Nature Climate\nChange, https:\/\/doi.org\/10.1038\/s41558-018-0203-0<\/a><\/p>\n\n\n\n Rau pers. comm. 1, 2018. Email to Brad\nWarren, Dec 4, 2018.<\/p>\n\n\n\n Rau pers. comm. 2, 2018. Email to\nGoogle Group discussion on CDR, Dec 24, 2018.<\/p>\n\n\n\n Smith et al 2016. Biophysical and\neconomic limits to negative CO2<\/sub> emissions. Nature Climate Change 6,\n42-50 (2016), https:\/\/www.nature.com\/articles\/nclimate2870<\/a> or https:\/\/core.ac.uk\/download\/pdf\/77052341.pdf<\/a>.<\/p>\n\n\n\n Snohomish County 1, undated. Grow Here, web page: https:\/\/snohomishcountywa.gov\/DocumentCenter\/View\/40707\/Agriculture?bidId=<\/a><\/p>\n\n\n\n Snohomish County 2, undated. Forest\nResource Lands Planning, Snohomish County Planning & Development Services,\nweb page: https:\/\/snohomishcountywa.gov\/1538\/Forest-Resource-Lands-Planning<\/a><\/p>\n\n\n\n Washington MRAC 2017. Addendum to Ocean Acidification: From Knowledge to Action. Washington State\u2019s Strategic Response. Washington Marine Resources Advisory Council. 2017, December 2017. http:\/\/oainwa.org\/assets\/docs\/2017_Addendum_BRP_Report_fullreport.pdf<\/a><\/p>\n\n\n\n <\/p>\n","protected":false},"excerpt":{"rendered":" Emerging tools for emissions drawdown on land and sea By Brad Warren, NFCC\/Global Ocean Health, Revised December 1st, 2019 For decades, failure to reduce carbon pollution has been a central conundrum for humankind, producing obvious consequences across both marine and … Continue reading ![\"\"](\"http:\/\/globaloceanhealth.org\/wp-content\/uploads\/2019\/12\/image.png\")
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FIGURE S.1. <\/strong>Scenario of the role of negative emissions technologies in reaching net zero emissions. NOTE: For any concentration and type of greenhouse gas (e.g. methane, perfluorocarbons, and nitrous oxide) CO2e signifies the concentration of CO2\u00a0which would have the same amount of radiative forcing. SOURCE: UNEP, 2017.
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SOURCE: <\/em>\u00a0Table 8.1 from National Academies 2018. <\/figcaption><\/figure>\n\n\n\n