Carbon cycle management with increased photo-synthesis and long-term sinks

Peter Read*

Introduction and Summary Conclusions from an Expert Workshop**

Energy related emissions are just over 5 per cent of CO₂ flows into and out of the atmosphere.  This suggests that mitigation investment in the heavily capitalised energy sector is likely to be less cost-effective than investment designed to increase photosynthesis on under-capitalised land. 

Managing land so as to substantially increase the total amount of terrestrial photosynthesis, and hence the supply of biomass, raises concerns related to the human ‘ecological footprint’.  These neglect the reality that natural ecosystems do not maximise the sustainable productivity of the land where they have evolved.  Such simple investments as stock-proof fencing to prevent animals destroying crops and plantations at the seedling stage can improve on nature.  Carbon fixing soil amendment yields environmental benefits, including enhanced fertility and water retention. 

Efficient management of part of the land, in lieu of widespread unsustainable traditional land management, can enable natural bio-diversity to flourish in conservation areas.  Such efficient management can yield food and forestry products co-produced with biomass on existing cropland.  Alternatively (and hence additionally) estimates of land requirements to effectively mitigate all current anthropogenic emissions of CO₂ fall well short of the ~1.5Gha of potential arable land (IPCC 2001) that is not in use – there is no shortage of land but of investment in land.  Additional biomass can be used in lieu of fossil fuel as the basis for bio-fuels and bio-electricity; its carbon content, in the form of bio-char (“charcoal”) can be used for soil amendment with ~5K-yr half life; or it can be used as wood, or advanced materials such as carbon fibre, in long-lived artefacts.   

On plausible technological assumptions and oil price projections, CO₂ reductions got from better use of land, and of products of the land, can have low or even negative cost, taking account of added value from co-products.  Done on a large enough scale, such better land use can contribute to rapid reductions in CO₂ levels if needed (~30ppm per decade) e.g. through bio-energy with CO₂ sequestration, involving the extra cost of CO₂ separation, compression and safe storage (CCS). 

This good news was considered in the context of potential abrupt climate change (ACC) at a recent expert workshop**- visit www.accstrategy.org .   No scenario was presented in which this threat was imminent, but it was recognised that climate models are more stable than the paleo-climatic record, that a failure of the THC might prove to be irreversible, and that processes of terrestrial ice loss, sea-ice variability, methane release and climate induced reduction of photosynthesis could precipitate imminent ACC, for which the thresholds and triggers are currently poorly understood.  In particular, there may be a limit to the heat burden that it is safe to inject into the oceans, which would mean that there is a time limit to the elevation of GHG levels above pre-industrial (this implies a misspecification of the ultimate objective at Article 2 of the Rio Convention). For such a limit to be met, carbon management needs to be capable of significant annual net absorption of CO₂ from the atmosphere.  This cannot be achieved by reliance on the zero-emissions energy technologies that are promoted through the emphasis on domestic action built in to the Kyoto Protocol.  At best those result in an asymptotic approach to the enhanced level in the natural sinks.  A negative emissions system is needed that can drive a linear downward path in the CO₂ level, e.g. by growing additional biomass and using it in ways that store part of its carbon content long term.

The conclusion of the workshop was that policymakers should be urged to stimulate the growth of a global bioenergy industry, with world trade (mainly ‘North-South’ trade) in liquid bio-fuels such as ethanol and synthetic (e.g. Fischer Tropsch) bio-diesel.  In the event scientific progress over the years ahead reveals, say in 2020, that a trigger for ACC is imminent, the existence of a large scale global bioenergy industry would put the world in much better shape to respond effectively. However, the growth of global bio-energy has so many near and medium term advantages that the abrupt climate change aspect comes last in the following list.

1. post 2012: more ambitious CO2 reductions are available at modest cost, with stabilisation by 2025 at 420ppm CO₂ practicable.
2. transportation emissions: bio-ethanol and bio-diesel are here-and-now technologies that can make an immediate impact on the otherwise intractable problem of vehicle emissions.
3. energy security: domestic supplies from advanced fermentation technology using cellulosic feedstock can provide USA and Europe with sufficient transportation fuels to meet essential needs.  Diversification of industrialised country imports to include ethanol and bio-diesel from developing counties will break OPEC’s market power.
4. farm support: a new source of income from biomass supply as bio-energy feedstock, co-produced with food by farmers in developed countries threatened by WTO decisions on export subsidies, along with woody feedstock co-produced with timber on non-arable (e.g. steep) land.  
5. development:  carbon credits to developing countries based on absorption of CO₂ in the production of biomass feedstock can support the development of bio-fuel production, hence cutting balance of payments costs of imported oil and eventually leading to sustainable growth, led by exports of ethanol and bio-diesel. Carbon credit funded investments can co-produce food and fuel, as in Brazil, where sugar cane ethanol is widely used in lieu of gasoline.
6. problems of Africa:  weak institutions and ill-defined land tenure entail a community based approach with tens of thousands of projects and major capacity building needed to train project leaders.  Exigent communities demand short-term pay-off such as can be got from techniques that raise soil fertility and water retention whilst sequestering carbon in the soil, as well as relieving energy poverty and yielding sustainable rural development.  There is no ‘silver bullet’ and a long-term effort is needed build capacity and to channel funding derived from energy consumers in the ‘North’ into appropriate local solutions.  In this way, addressing Africa’s problems and responding to the threat of ACC can go hand in hand
7. abrupt climate change: if linked to CCS (carbon capture and sequestration technology being developed in the USA to yield ‘clean coal’) bio-energy becomes a ‘negative emissions energy system’ with photo-synthesis of biomass absorbing CO₂ and CCS preventing its return to atmosphere when the bio-fuel is combusted.  Under policy urgency from new scientific evidence, in 2020 say, of imminent abrupt climate change, this can get the CO₂ level down to the pre-industrial level of 280ppm by around 2060.

Key papers underpinning the workshop’s conclusions

Not all these papers were presented at the workshop.  1 and 2 were first presented at the International Energy Workshop, IIASA, 2003 and are now forthcoming in the peer-reviewed literature.  3 is an NRDC Report currently in draft.  4 through 7 were presented at the workshop and 8 was in preparation at that time – visit www.accstrategy.org . their suitability for linking to carbon capture and sequestration systems in the event of imminent ACC.  The potential for dual-fired fossil and bio-fuelled systems in a low risk transitional approach is noted.

1. Read. P. and J..Lermit. “Bio-Energy with Carbon Storage (BECS): a Sequential Decision Approach to the threat of Abrupt Climate Change” Energy (forthcoming: www.sciencedirect.com, ref EGY 1413).
   Models the inter-related markets for fuel,  woody fibre and land on a global scale over a 70 year time horizon to simulate the effect of using additional land for conventional forestry and for short rotation energy crops relative to familiar reference scenarios (IS92 business as usual, Tellus Institute’s fossil free energy scenario, and a notional ‘Kyoto’ midway between) in two cases, first continued expectation of gradual climate change, and second, bad news of imminent ACC in ~2020.  Under the first case, low cost CO₂ stabilisation (possibly negative cost if peak oil induces rapidly rising fossil fuel prices) is achieved at a level below 420ppm, with an initial long rotation storing carbon for a few decades, while energy sector capital stock adjusts to achieve a smooth transition to using bio-energy.  Under the second case conditions of ACC-driven urgency, the long rotation land is turned over to energy cropping and ‘maximal’ land use change, along with accelerated technological progress, results in the substantial dominance of bio-energy by mid-century, whilst CO₂ decreases rapidly to the pre-industrial level of 280ppm through the (likely costly) linking of all point source emitters, both fossil and bio-fuel, to carbon capture and sequestration.      
2. Day, D., R.J. Evans, J.W. Lee and D. Reicosky. “Economical CO2, SOx and NOx capture from fossil fuel utilization with combined renewable hydrogen productionand large scale carbon sequestration” Energy (forthcoming: www.sciencedirect.com, ref EGY 1407).
   Explores an advanced (patent pending) process for producing a novel nitrogen-enriched slow release carbon-sequestering fertilizer.  Biomass wastes from forestry and agriculture are pyrolyzed, with reforming of volatile fractions to hydrogen. Temperature is controlled to yield a char with affinity for CO₂, SOx and Nox, which are absorbed from fossil fuel flue gases into the pore structure of the char to form the slow release fertilizer.  Apart from fertilization, the material provides a substrate congenial to the microbial and fungal activity that facilitates the transport of soil nutrients to rootlets, whilst the slow release feature reduces leaching and polluted run-off.  From a systems perspective, the CO₂ impact cf fossil fuels is –112 kg/GJ compared with +48 kg/GJ for natural gas and +80kg/GJ for coal.  Applied to current global bio-energy usage of ~55EJ, this process would absorb ~6Gt CO₂ without taking account of the dynamic hold-up of carbon in the larger volume of biomass growing on the fertilized soils.
3. Greene, N. and 13 others from Princeton University, Dartmouth College, UCS, ORNL, Michigan State University and NRDC .“Growing Energy: how biofuels can help end America’s oil dependence”
   Analyzes novel integrated systems of alternative mature technologies on existing US cropland to produce biomass for energy production with current food production maintained.  ‘Consolidated bio-processing’ of the cellulosic fraction of crops – in which hydrolysis and fermentation occur in a single process step – is applied to high productivity switchgrass feedstock.  One of the most promising options extracts protein, ferments ethanol, and co-produces electricity. Among the scenarios analyzed, this one yields the lowest cost transport fuel at $0.56/USgal of gasoline equivalent, with co-produced protein valued equal to the long term average for soy meal protein of $0.20 per pound and power valued at $0.04/kWh.  This assumes a 20kton per day plant and technological progress to 2025, when the USDoE forecast gasoline prices in the range $0.48 – 1.03/gal around a base case of $0.79/gal.  As with paper 1, co-production is key to the potential cost-competitiveness of bio-energy systems.  In aggregate, about half of current US demand for transportation fuels could, with foreseeable advances in technology, be met in 2025 from biomass produced on existing US cropland, along with the same amount of food as is currently produced. With improved vehicle efficiency and smart urban growth, gasoline demand could potentially be reduced to zero.
4. Faaij, A. “Modern options for producing secondary energy carriers from biomass”
   Reviews the variety of existing commercial bio-energy technologies for meeting demands for heat electricity and transportation fuels, their near-term expected development and long-term prospects confirming the technological assumptions that underlie other papers in this set (1, 3, 5and 6) and discusses
5. Moreira. J.R. “Global biomass energy potential”
   Evaluates potential of tropical and sub-tropical cropland for the production of sugar-cane and its conversion to ethanol and electric power at an intensity equivalent to the author’s home region in Brazil, i.e. ~7per cent of all such cropland.  With the use of only 143mHa, and with prospective technological advances, 164EJ of primary energy and 90EJ of ethanol and electricity can be produced from 4000 units of a scale similar to the largest existing in Brazil, with the creation of ‘millions of direct and indirect jobs”.  This implies that the utilization of 20 per cent of tropical potential cropland in this way would meet all current global commercial energy demands.  This is additive to production from energy forest plantations envisaged in Paper 1, involving less fertile land, and suggests the export potential of advanced developing countries.
6. Hemstock, S. and J. Woods. “Bio-energy systems at the community level”
   Adopting a ‘no one size fits all’ philosophy, reviews issues of scale, human capacity, community involvement, technology and critical mass in the development of bio-energy on three small island states.  Shows the need for an integrated, multi-disciplinary, cross-sectoral – i.e. ‘whole systems’ – approach with strong and consistent policy signals and support systems to enable the potential of bio-energy to be realised in the subsistence economies to be found in the rural sectors of the LDC’s.  The existence of a global market for bio-fuels would provide eventual linkage to the market economy but initial deployment of appropriate technologies like anaerobic digestion and small scale biodiesel is needed to meet local needs.
7. Ogawa, M, Y Okimori, and F Takahashi “Sustainability and reality of the projects of carbon sequestration by carbonization and forestation (cfc) as a biomass conversion option”
   Reports on three examples of bio-char sequestration projects: disposing of urban and rural wastes (in Japan) soil improvement for mallee eucalypt agro-forestry to suppress saline water intrusion (in Australia – JI project) and for disposal of pulp mill wastes (in Indonesia – CDM project).  Reports improved soil productivity and other socio-economic benefits from these projects.
8. Lehmann, J., J. Gaunt and M. Rondon. “Bio-char sequestration in terrestrial ecosystems”
   Makes the first attempt to assess the macro-potential of bio-char soil amendment (apart from this author’s back-of -envelope arithmetic at the Workshop).  Reviews several cases: a change from slash and burn to slash and char, improved ‘charcoal’ production, agricultural waste recycling, and current bio-energy respectively yielding .2, .02, .16 and .2GtC/yr  sequestered.  However, the expansion of modern bio-energy in line with a range of scenarios could yield 5.5 – 9.5 GtC/yr, sufficient to sequester all current emissions.

Comment

It could be that climate change policy has been misled by a plausible fallacy – that the energy sector’s problem is best cured in the energy sector.  This possibility is revealed by the emergence of two technologies for long-term disposal of carbon fixed by increased photosynthesis (CCS and bio-char soil amendment).  It appears that (along with the industrial practicability and here-and-now availability of bio-energy systems) the GHG mitigating potential of photosynthesis has been overlooked by a policy-making community that has focused on capping energy sector emissions rather than on a technology-based approach to managing carbon.  The environmental and socio-economic benefits from an integrated approach to managing carbon may turn out to be such that bio-energy comes to dominate the market, with ambient energy technologies (wind, wave and non-photosynthetic solar) having a smaller role than widely envisaged.  However, this possibility should not lead to the putting of all eggs in the bio-energy basket: resistance to rational land use may turn out to be very great; technological progress with biomass production and conversion may prove disappointing; population trends may put greater pressure on land than is currently projected; etc.  But it is clear that a great many ends could be served by doing as much with bio-energy, and world trade in bio-fuels, as may be.  Prima facie it appears eminently negotiable, with energy security for the USA, lowered farm support costs for the EU, and sustainable development with ended energy poverty for many land rich but otherwise impoverished members of G77.

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*        Peter Read is Senior Research Officer with the Economics Department at Massey University, New Zealand. 

**     Convened in Paris last October by this author, with the support of the Better World Fund of the United Nations Foundation at the behest of former IPCC Chairman Dr Robert Watson, with mission statement to “address the policy implications of potential abrupt climate change”.  Unfortunately, connected editorial work led this author to overlook early announcements of this Hadley Centre Symposium and I am grateful to the organizers for the flexibility they have shown in accepting this last minute offering.