Cost-effective Greenhouse Gas Research Articles

Rewetting on agricultural peatlands can offer cost effective greenhouse gas reduction at the national level

To reach EU’s carbon neutrality target by 2050, emission reductions in the land-use sector are needed. Agricultural peatlands attribute for half of the greenhouse gas emissions of cropland in both in EU and Finland. High greenhouse gas emissions from agricultural peatlands are primarily caused by CO2 emissions following aerobic peat decomposition due to deep drainage, and studies have shown that raising water-table has potential to slow down the decomposition process. Here we studied the emission reduction potential and cost of implementing controlled drainage, paludiculture, peatland restoration and afforestation to current land use on agricultural peatlands in Finland. We created three scenarios with increasing amount of wet field use on cultivated organic soils and estimated their effects on national greenhouse gas emissions and farmers’ income. The yearly emission reduction ranged from 0.3 to 5.0 Mt CO2 equivalents in the different scenarios compared to the current state in Finland. Emission reductive land use had a negative impact on the farmers income, which should be compensated. Assuming the government compensates the lost income for the farmers, the cost of emission reduction ranged from −4 to 45 € per ton of CO2 equivalents. Rewetting provided the most emission reduction per area and was the most cost effective. We conclude that substantial emission reduction is attainable by rewetting agricultural peatlands. The cost of emission reduction is inexpensive compared to average carbon price in European Union emission trading system, or to the costs of technical carbon capture and storage in Finland.

Opportunities beyond net-zero CO2 for cost-effective greenhouse gas mitigation in China

Achieving net-zero CO2 emissions is the current main focus of China’s carbon neutrality goal. However, non-CO2 greenhouse gases (GHGs) are more powerful climate forcers, making their emission reduction an opportunity to rapidly mitigate future warming. Here, we evaluate non-CO2 mitigation potentials, costs and climate benefits in the context of China’s carbon neutrality goals. The assessment is conducted by coupling the integrated assessment model GCAM with a climate emulator. The findings indicate that mitigation technologies can largely reduce fluorinated gas emissions from industrial sectors, but long-term non-CO2 reductions of energy sector activities rely heavily on fuel switching. Furthermore, the cumulative costs of deploying non-CO2 mitigation technologies are projected to be less than 10% of the total costs of achieving carbon neutrality from 2020 to 2060. If non-CO2 mitigation measures are included in the overall mitigation portfolio, the benefits of avoided warming would by far outweigh the total mitigation cost increase. Our results thus highlight that incorporating a wider suite of GHGs into climate change mitigation strategies can enhance the cost-effectiveness of mitigation efforts.

Constraining the effectiveness of inherent tracers of captured CO2 for tracing CO2 leakage: Demonstration in a controlled release site

Geological storage of carbon dioxide (CO2) is an integral component of cost-effective greenhouse gas emissions reduction scenarios. However, a robust monitoring regime is necessary for public and regulatory assurance that any leakage from a storage site can be detected. Here, we present the results from a controlled CO2 release experiment undertaken at the K-COSEM test site (South Korea) with the aim of demonstrating the effectiveness of the inherent tracer fingerprints (noble gases, δ13C) in monitoring CO2 leakage. Following injection of 396 kg CO2(g) into a shallow aquifer, gas release was monitored for 2 months in gas/water phases in and above the injection zone. The injection event resulted in negative concentration changes of the dissolved gases, attributed to the stripping action of the depleted CO2. Measured fingerprints from inherent noble gases successfully identified solubility-trapping of the injected CO2 within the shallow aquifer. The δ13C within the shallow aquifer could not resolve the level of gas trapping, due to the interaction with heterogeneous carbonate sources in the shallow aquifer. The time-series monitoring of δ13CDIC and dissolved gases detected the stripping action of injected CO2(g), which can provide an early warning of CO2 arrival. This study highlights that inherent noble gases can effectively trace the upwardly migrating and fate of CO2 within a shallow aquifer.

Electrification of multi-energy hubs under limited electricity supply: De-/centralized investment and operation for cost-effective greenhouse gas mitigation

• Decarbonization via electrification is effective, economic, advisable, challenging. • Limited centralized electricity alters optimal design of new de-/centralized assets. • Multi-objective MILP finds pareto-optimal V2G EVs and mix of converters, storages. • Full year hourly resolution allows for detailed grid and asset operational analysis. • Cost and emission breakdown reveal dominance of embodied emission and upfront cost. Electrification of residential's heating and private mobility is often seen as a cure-all solution to the sector's immense greenhouse gas (GHG) emission problem. However, the necessary supply of affordable, secure, and sustainable centralized electricity is commonly assumed unlimited in related planning efforts. Hence, it remains unclear how beneficial electrification is under limited supply. Therefore, we investigate how jointly planned de-/centralized asset upgrades and Vehicle-2-Home enabled electric vehicles can overcome such limitations exemplarily for five residential building types in Switzerland. Thereto, the proposed, novel optimizations of Multi-energy Systems based on the Energy Hub concept, which extend the classical decentralized Energy Hub perspective to include investments into centralized assets, simultaneously select, design, and operate such assets and vehicles to minimize lifecycle-emissions and -costs while covering thermal, electrical and mobility demands under scenarios of A) unlimited, B) three partially limited, and C) no (stand-alone) centralized electricity. The optimizations prove the centralized supply limitations to be crucial, as achievable CO 2eq mitigations halve on average from A) >60% over B) 45% to only C) 30%. Further, a substantially altered and wide mix of assets is optimal to overcome the identified sole supply bottleneck of electrical energy scarcity during winter. Transitioning from low-cost to low-emission solutions, natural gas based centralized gas turbines and decentralized combined heat and power plants (CHPPs) combined with air-source heat pumps are displaced by biogas CHPPs, ground source heat pumps and centralized photovoltaics, while local photovoltaics and Vehicle-2-Home usage are constants. Surprisingly, all partially limited scenarios including nuclear phase-out and additional cross-border electricity trade stops yield similar results, which enable emission mitigations of 50% over the non-electrified reference without additional annualized cost. Stronger emission mitigation proves prohibitively costly. Overall, considering limited supply avoids overestimation of achievable emission mitigation, underestimation of total costs as well as identification of too simplistic asset portfolios.

On the cost-effectiveness of national economy-wide greenhouse gas emissions abatement measures

This paper explores cost-effective greenhouse gas abatement options for the European Union Member State of Cyprus, for those sectors of the national economy that are not subject to the European Emissions Trading System. The analysis leads to the construction of a baseline and several alternative marginal emission abatement cost curves. It addresses all economic sectors and considers all different types of mitigation measures – improving energy efficiency, switching to low- or zero-carbon fuels, and inducing behavioural change towards public transport modes. We apply nationally appropriate data that are mainly derived from local market information and judgement of national experts. Finally, we present results of several sensitivity analyses, which address main shortcomings of marginal abatement cost curves that have been identified in the literature, and discuss the policy implications of each one of them. Apart from its relevance for EU Member States, this assessment is useful for all countries seeking guidance in their decarbonisation strategies.

Prioritizing among the end uses of excess renewable energy for cost-effective greenhouse gas emission reductions

Preventing the curtailment of excess renewable generation, caused by mismatches between variable renewable electricity generation and the electric load, is a key strategy for maximizing greenhouse gas emissions reductions by integrating renewable resources into the electric grid. Strategies to harness excess renewable generation for useful purposes exist, but it is unclear which of these end uses provides the most effective use of available excess generation to maximize greenhouse gas emissions reductions in a cost-effective manner. This study investigates and compares three end-use strategies for utilizing excess renewable generation – storage in electrical energy storage systems, production of transportation fuel or vehicle charging, or production of renewable gas – and their diverse technology pathways on the bases of their greenhouse gas emissions reduction potential and the impacts of their implementation on the cost of energy services. This is accomplished by modeling the integration of 46 different technology pathways for using excess renewable generation in a 70% renewable and an 80% renewable electric grid configuration during the year 2050 in California using the Holistic Grid Resource Integration and Deployment (HiGRID) platform, which is a temporally-resolved resource dispatch model of the electricity system. Technology and cost characteristics for batteries, hydrogen energy storage systems, vehicle fueling or charging, and renewable gas production technologies are collected from multiple sources and their effect on reducing greenhouse gas emissions and affecting the Levelized Cost of Energy (LCOE) services in the HiGRID platform are examined. It was discovered that using excess renewable generation to produce transportation fuel for hydrogen vehicles or to charge electric vehicles provided the largest total greenhouse gas emissions reductions and lowest per-ton cost of greenhouse gas reduction. Use in grid energy storage and production of renewable gas provided similar but relatively lower total greenhouse gas reductions than transportation, with the latter imposing lower per-ton costs of greenhouse gas reduction. More generally, greenhouse gas reduction potential of these end uses depended on the intensity of the fuel being displaced by renewables, while LCOE effects depended on the temporal flexibility of the technologies associated with this end use. Overall, this study provides insight into a priority order for directing the use of excess renewable generation towards end uses to achieve greenhouse gas reduction goals such as those in California in a cost-minimal manner, and investigates the sensitivities that influence the effectiveness of these end uses.

Marginal abatement cost curves for agricultural climate policy: State-of-the art, lessons learnt and future potential

Abstract Combatting climate change has risen to the top of the international policy discourse. Effective governance necessitates the generation of concise information on the costs-effectiveness of policy instruments aimed at reducing atmospheric greenhouse gas (GHG) emissions. The marginal abatement cost curve (MACC) approach is a framework commonly used to summarise information of potential mitigation effort, and can help in identifying the most cost-effective managerial and technological GHG mitigation options. Agriculture offers key opportunities to mitigate GHG emissions and utilise carbon (C) sink potentials. Therefore, a number of countries have developed national agricultural MACCs in the last decade. Whilst these MACCs have undoubtedly been catalysers for the information exchange between science and policy, they have also accentuated a range of constraints and limitations. In response, each of the scientific teams developed solutions in an attempt to address one or more of these limitations. These solutions represent ‘lessons learned’ which are invaluable for the development of future MACCs. To consolidate and harness this knowledge that has heretofore been dispersed across countries, this paper reviews the engineering agricultural MACCs developed in European countries. We collate the state-of-the-art, review the lessons learnt, and provide a more coherent framework for countries or research groups embarking on a trajectory to develop an agricultural MACC that assesses mitigations both within the farm gate and to the wider bioeconomy. We highlight the contemporary methodological developments, specifically on 1) the emergence of stratified MACCs; 2) accounting for soil carbon sequestration 3) accounting for upstream and downstream emissions; 4) the development of comprehensive cost-calculations; 5) accounting for environmental co-effects and 6) uncertainty analyses. We subsequently discuss how the mitigation potential summarised by MACCs can be incentivised in practice and how this mitigation can be captured in national inventories. We conclude that the main purpose of engineering MACCs is not necessarily the accurate prediction of the total abatement potential and associated costs, but rather the provision of a coherent forum for the complex discussions surrounding agricultural GHG mitigation, and to visualise opportunities and low-hanging fruit in a single graphic and manuscript.

Water Quality Management and Climate Change Mitigation: Cost-effectiveness of Joint Implementation in the Baltic Sea Region

This paper explores the scope for simultaneously managing nutrient abatement and climate change mitigation in the Baltic Sea (BS) region through the implementation of a selection of measures. The analysis is undertaken using a cost-minimisation model for the entire BS region, the BALTCOST model. In the present research, the model has been extended to include greenhouse gas (GHG) emissions effects, enabling us to analyse the trade-offs between cost-effective GHG and nutrient load reductions. We run the model for four different scenarios in order to compare the environmental and economic consequences of contrasting strategies: single environmental objective management versus joint implementation strategy. The results show that implementing land-based measures with a sole focus on water quality (to meet the HELCOM's 2013 Baltic Sea Action Plan nutrient abatement targets) can produce climate change mitigation co-benefits equivalent to 2.3% of the 2005 emission level (from agriculture and waste water combined) for the entirety of the BS region. More interestingly, a joint implementation strategy can deliver further climate change mitigation benefit (i.e. up to 5.4%) at a marginal cost that is comparable to mitigation costs reported by other studies for efficient technologies. All in all the results demonstrate that a joint strategy to improve water quality and to reduce climate change is economically beneficial. Our findings show that the cost and the outcome of the implementation vary between countries. This illustrates the need to develop a joint regional policy for water and climate regulation that fully considers the asymmetry in both the expected effects and cost distribution across the countries in the region.

Cost effective greenhouse gas reductions in the steel industry from an Organic Rankine Cycle

Large quantities of low grade heat (LGH) are genera ted within many process industries, and the recovery of LGH is a potentially significan t means of improving process efficiency, but it is often difficult to find an ap propriate internal heat load. One alternative is to use appropriate technologies to c onvert the low grade heat to electricity for use on site. This paper describes the environme ntal and techno-economic evaluation of a case study examining the potential application of an Organic Rankine Cycle (ORC) to generate electricity from LGH from the stacks of a coke oven used in steel production. 21 MW of LGH was available for recovery at the plant and resource accounting and lifecycle analysis methods were used to evaluate the environmental and economic benefits of the operation of an ORC. The r esults showed that between 1 and 3% of the CO 2 emitted directly through the production of coke wo uld be offset by installation of an ORC, with lifecycle environmenta l impacts of coke production reduced by less than 1%, although this was sufficie nt to offset over 10,000 t CO 2 annually. However, the amount of electricity gener ated was sufficient to replace all currently imported electricity and economic analysi s indicated a relatively attractive discounted payback period of between 3 and 6 years, suggesting this may be a commercially viable option, which could present a r elatively cost effective method of achieving greenhouse gas savings in the process ind ustries.

Developing farm-specific marginal abatement cost curves: Cost-effective greenhouse gas mitigation opportunities in sheep farming systems

Growing demand for agricultural produce, coupled with ambitious targets for greenhouse gas emissions reduction present the scientific, policy and agricultural sectors with a substantial mitigation challenge. Identification and implementation of suitable mitigation measures is driven by both the measures’ effectiveness and cost of implementation. Marginal abatement cost curves (MACCs) provide a simple graphical representation of the abatement potential and cost-effectiveness of mitigation measures to aid policy decision-making. Accounting for heterogeneity in farm conditions and subsequent abatement potentials in mitigation policy is problematic, and may be aided by the development of tailored MACCs. Robust MACC development is currently lacking for mitigation measures appropriate to sheep systems. This study constructed farm-specific MACCs for a lowland, upland and hill sheep farm in the UK. The stand-alone mitigation potential of six measures was modelled, against real farm baselines, according to assumed impacts on emissions and productivity. The MACCs revealed the potential for negative cost emissions’ abatement in the sheep industry. Improving ewe nutrition to increase lamb survival offered considerable abatement potential at a negative cost to the farmers across all farms while, lambing as yearlings offered negative cost abatement potential on lowland and upland farms. The results broadly advocate maximising lamb output from existing inputs on all farm categories, and highlight the importance of productivity and efficiency as influential drivers of emissions abatement in the sector. The abatement potentials and marginal costs of other measures (e.g. reducing mineral fertiliser use and selecting pasture plants bred to minimise dietary nitrogen losses) varied between farms, and this heterogeneity was more frequently attributable to differences in individual farm management than land classification. This has important implications for the high level policy sector as no two farms are likely to benefit from a generic one size fits all approach to mitigation. The construction of further case-study farm MACCs under varying farm conditions is required to define the biophysical and management conditions that each measure is most suited to, generating a more tailored set of sector-specific mitigation parameters.

Maximizing the greenhouse gas reductions from biomass: The role of life cycle assessment

Biomass can deliver significant greenhouse gas reductions in electricity, heat and transport fuel supply. However, our biomass resource is limited and should be used to deliver the most strategic and significant impacts. The relative greenhouse gas reduction merits of different bioenergy systems (for electricity, heat, chemical and biochar production) were examined on a common, scientific basis using consistent life cycle assessment methodology, scope of system and assumptions. The results show that bioenergy delivers substantial and cost-effective greenhouse gas reductions. Large scale electricity systems deliver the largest absolute reductions in greenhouse gases per unit of energy generated, while medium scale wood chip district heating boilers result in the highest level of greenhouse gas reductions per unit of harvested biomass. However, ammonia and biochar systems deliver the most cost effective carbon reductions, while biochar systems potentially deliver the highest greenhouse gas reductions per unit area of land.The system that achieves the largest reduction in greenhouse gases per unit of energy does not also deliver the highest greenhouse gas reduction per unit of biomass. So policy mechanisms that incentivize the reductions in the carbon intensity of energy may not result in the best use of the available resource.Life cycle assessment (LCA) is a flexible tool that can be used to answer a wide variety of different policy-relevant, LCA “questions”, but it is essential that care is taken to formulate the actual question being asked and adapt the LCA methodology to suit the context and objective.

Energy efficiency improvement and GHG abatement in the global production of primary aluminium

Primary aluminium production is a highly energy-intensive and greenhouse gas (GHG)-emitting process responsible for about 1 % of global GHG emissions. In 2009, the two most energy-intensive processes in primary aluminium production, alumina refining and aluminium smelting consumed 3.1 EJ, of which 2 EJ was electricity for aluminium smelting, about 8 % of the electricity use in the global industrial sector. The demand for aluminium is expected to increase significantly over the next decades, continuing the upward trend in energy use and GHGs. The wide implementation of energy efficiency measures can cut down GHG emissions and assist in the transition towards a more sustainable primary aluminium industry. In this study, 22 currently available energy efficiency measures are assessed, and cost-supply curves are constructed to determine the technical and the cost-effective energy and GHG savings potentials. The implementation of all measures was estimated to reduce the 2050 primary energy use by 31 % in alumina refining and by 9 % in primary aluminium production (excluding alumina refining) when compared to a “frozen efficiency” scenario. When compared to a “business-as-usual” (BAU) scenario, the identified energy savings potentials are lower, 12 and 0.9 % for alumina refining and primary aluminium production (excluding alumina refining), respectively. Currently available technologies have the potential to significantly reduce the energy use for alumina refining while in the case of aluminium smelting, if no new technologies become available in the future, the energy and GHG savings potentials will be limited.

Low-carbon buildings, health and wellbeing: Current perspectives and critical challenges

This Special Issue of Indoor and Built Environment addresses health and wellbeing within the context of the current drive for ‘low-carbon’ buildings – where the term ‘low-carbon’ is used here to include zero or nearly zero carbon/energy approaches. Papers are mainly from invited authors, and a few are extended versions drawn from a relevant Conference of the UK Indoor Environments Group (UKIEG) held in June 2013. All papers were subject to the journal’s peerreview process from authoritative independent experts. Whilst the focus is primarily on the United Kingdom and Europe, and especially on heating-dominated countries, many lessons/issues are also broadly applicable to other climates and regions. This introductory Editorial provides a background overview of the topic, discusses key themes emerging from the papers and argues that the lack in joined-up thinking in the climate change and health policy agendas requires researchers to urgently address one of the main challenges in this field – namely how to ‘sell’ the importance and value of addressing complexity and uncertainty. The intrinsically complex nature of the relationship between health/wellbeing and low-carbon buildings has been discussed for some time in various contexts. Various communities have debated the matter, including the UK Indoor Environments Group (UKIEG), a multidisciplinary network of academic, policy makers and industry concerned with the quality of indoor environments – especially from a health and wellbeing perspective. UKIEG members – some of whom are authors of papers in this Special Issue and have presented at our Conferences – have debated the topic(s) of this Special Issue several times since the UKIEG’s foundation in 2003. These debates have often been accompanied by a great deal of frustration amongst concerns of: (1) a disconnect between the health and the energy/carbon policies; (2) a lack of suitable evidence that current trajectories for low-carbon buildings are sufficiently robust and will provide ‘healthy’ indoor environments (or at least as healthy as current environments). Thus, this Special Issue is timely, not only as a formal contribution to those debates occurring within the UKIEG and other similar groups worldwide, but also because the implementation of the low-carbon buildings agenda is gaining momentum in several countries, both for new builds and retrofits. This means that the question of whether low-carbon buildings are more/ less conducive to health and wellbeing must be addressed urgently. Also, in the past couple of years the first mainstream low-carbon buildings (as opposed to isolated prototypes) have been constructed and inhabited, representing a fantastic opportunity to study the issue in situ. Buildings are responsible for more than 40% of global energy use and one-third of global greenhouse gas emissions both in developed and developing countries. Furthermore, the Building Sector has a large potential for delivering long-term, significant and cost-effective greenhouse gas emission reductions. Consequently, most developed countries and many developing countries have already taken steps to address emissions from the Building Sector, mainly in the form of legislation dictating minimum carbon/ energy standards – especially (but not solely) for new buildings and major renovations. For example, the European Union (EU) ‘Energy Performance of Buildings Directive’ was first published in 2002 (Directive 2002/91/EC), requiring all EU countries to enhance their building regulations and to introduce energy certification schemes for buildings, as well as inspections of boilers and air-conditioners. A further version of the Directive published in 2010 (Directive 2010/31/EU) also included, amongst other things, a move towards new and retrofitted nearly zero energy buildings. As highlighted by several authors in this Issue, the drive for new low-carbon design paradigms

Water Loss Control Using Pressure Management: Life-cycle Energy and Air Emission Effects

Pressure management is one cost-effective and efficient strategy for controlling water distribution losses. This paper evaluates the life-cycle energy use and emissions for pressure management zones in Philadelphia, Pennsylvania, and Halifax, Nova Scotia. It compares water savings using fixed-outlet and flow-modulated pressure control to performance without pressure control, considering the embedded electricity and chemical consumption in the lost water, manufacture of pipe and fittings to repair breaks caused by excess pressure, and pressure management. The resulting energy and emissions savings are significant. The Philadelphia and Halifax utilities both avoid approximately 130 million liters in water losses annually using flow-modulated pressure management. The conserved energy was 780 GJ and 1900 GJ while avoided greenhouse gas emissions were 50 Mg and 170 Mg a year by Philadelphia and Halifax, respectively. The life-cycle financial and environmental performance of pressure management systems compares favorably to the traditional demand management strategy of installing low-flow toilets. The energy savings may also translate to cost-effective greenhouse gas emission reductions depending on the energy mix used, an important advantage in areas where water and energy are constrained and/or expensive and greenhouse gas emissions are regulated as in California, for example.

Electricity Production from Anaerobic Digestion of Household Organic Waste in Ontario: Techno-Economic and GHG Emission Analyses

The first Feed-in-Tariff (FiT) program in North America was recently implemented in Ontario, Canada to stimulate the generation of electricity from renewable sources. The life cycle greenhouse gas (GHG) emissions and economics of electricity generation through anaerobic digestion (AD) of household source-separated organic waste (HSSOW) are investigated within the FiT program. AD can potentially provide considerable GHG emission reductions (up to 1 t CO(2)eq/t HSSOW) at relatively low to moderate cost (-$35 to 160/t CO(2)eq) by displacing fossil electricity and preventing the emission of landfill gas. It is a cost-effective GHG mitigation option compared to some other FiT technologies (e.g., wind, solar photovoltaic) and provides unique additional benefits (waste diversion, nutrient recycling). The combination of electricity sales at a premium rate, savings in waste management costs, and economies of scale allow AD facilities processing >30,000 t/yr to be cost-competitive against landfilling. However, the FiT does not sufficiently support smaller-scale facilities that are needed as a transition to larger, more economically viable facilities. Refocusing of the FiT program and waste policies are needed to support the adoption of AD of HSSOW, which has not yet been developed in the Province, while more costly technologies (e.g., photovoltaic) have been deployed.

Greenhouse gas accounting for inventory, emissions trading and life cycle assessment in the land-based sector: a review

Governments, organisations and individuals have recognised the need to reduce their greenhouse gas (GHG) emissions. To identify where savings can be made, and to monitor progress in reducing emissions, we need methodologies to quantify GHG emissions and sequestration. Through the Australian Government’s Carbon Farming Initiative (CFI) landholders may generate credits for reducing emissions and/or sequestering carbon (C). National GHG inventories for the United Nations Framework Convention on Climate Change, and accounting under the Kyoto Protocol use a sectoral approach. For example, fuel use in agriculture is reported in the transport component of the energy sector; energy use in producing herbicide and fertiliser is included in the manufacturing section of the energy sector; sequestration in farm forestry is reported in the land use, land-use change and forestry sector, while emissions reported in the agriculture sector include methane (CH4) from ruminant livestock, nitrous oxide (N2O) from soils, and non-carbon dioxide (CO2) GHG from stubble and savannah burning. In contrast, project-level accounting for CFI includes land-use change, forestry and agricultural sector emissions, and significant direct inputs such as diesel and electricity. A C footprint calculation uses a life cycle approach, including all the emissions associated with an organisation, activity or product. The C footprint of a food product includes the upstream emissions from manufacturing fertiliser and other inputs, fuel use in farming operations, transport, processing and packaging, distribution to consumers, electricity use in refrigeration and food preparation, and waste disposal. Methods used to estimate emissions range from simple empirical emissions factors, to complex process-based models. Methods developed for inventory and emissions trading must balance the need for sufficient accuracy to give confidence to the market, with practical aspects such as ease and expense of data collection. Requirements for frequent on-ground monitoring and third party verification of soil C or livestock CH4 estimates, for example, may incur costs that would negate the financial benefit of credits earned, and could also generate additional GHG emissions. Research is required to develop practical on-farm measures of CH4 and N2O, and methods to quantify C in environmental plantings, agricultural soils and rangeland ecosystems, to improve models for estimation and prediction of GHG emissions, and enable baseline assessment. There is a need for whole-farm level estimation tools that accommodate regional and management differences in emissions and sequestration to support landholders in managing net emissions from their farming enterprises. These on-farm ‘bottom-up’ accounting tools must align with the ‘top-down’ national account. To facilitate assessment of C footprints for food and fibre products, Australia also needs a comprehensive life cycle inventory database. This paper reviews current methods and approaches used for quantifying GHG emissions for the land-based sectors in the context of emissions reporting, emissions trading and C footprinting, and proposes possible improvements. We emphasise that cost-effective yet credible GHG estimation methods are needed to encourage participation in voluntary offset schemes such as the CFI, and thereby achieve maximum mitigation in the land-based sector.

Effects of Cattle Slurry Acidification on Ammonia and Methane Evolution during Storage

Slurry acidification before storage is known to reduce NH(3) emissions, but recent observations have indicated that CH(4) emissions are also reduced. We investigated the evolution of CH(4) from fresh and aged cattle slurry during 3 mo of storage as influenced by pH adjustment to 5.5 with sulfuric acid. In a third storage experiment, cattle slurry acidified with commercial equipment on two farms was incubated. In the manipulation experiments, effects of acid and sulfate were distinguished by adding hydrochloric acid and potassium sulfate separately or in combination, rather than sulfuric acid. In one experiment sulfur was also added to slurry as the amino acid methionine in separate treatments. In each treatment 20-kg portions of slurry (n = 4) were stored for 95 d. All samples were subsampled nine to 10 times for determination of NH(3) and CH(4) evolution rates using a 2-L flow-through system. In all experiments, the pH of acidified cattle slurry increased gradually to between 6.5 and 7. Acidification of slurry reduced the evolution of CH(4) by 67 to 87%. The greatest reduction was observed with aged cattle slurry, which had a much higher potential for CH(4) production than fresh slurry. Sulfate and methionine amendment to cattle slurry without pH adjustment also significantly inhibited methanogenesis, probably as a result of sulfide production. The study suggests that complex microbial interactions involving sulfur transformations and pH determine the potential for CH(4) emission during storage of cattle slurry, and that slurry acidification may be a cost-effective greenhouse gas mitigation option.

Bioethanol production from sugarcane and emissions of greenhouse gases - known and unknowns

Bioethanol production from sugarcane is discussed as an alternative energy source to reduce dependencies of regional economies on fossil fuels. Even though bioethanol production from sugarcane is considered to be a beneficial and cost-effective greenhouse gas (GHG) mitigation strategy, it is still a matter of controversy due to insufficient information on the total GHG balance of this system. Aside from the necessity to account for the impact of land use change (LUC), soil N2O emissions during sugarcane production and emissions of GHG due to preharvest burning may significantly impact the GHG balance. Based on a thorough literature review, we show that direct N2O emissions from sugarcane fields due to nitrogen (N) fertilization result in an emission factor of 3.87 � 1.16% which is much higher than suggested by IPCC (1%). N2O emissions from N fertilization accounted for 40% of the total GHG emissions from ethanol–sugarcane production, with an additional 17% from trash burning. If LUC-related GHG emissions are considered, the total GHG balance turns negative mainly due to vegetation carbon losses. Our study also shows that major gaps in knowledge still exist about GHG sources related to agricultural management during sugarcane production, e.g. effects of irrigation, vinasse and filter cake application. Therefore, more studies are needed to assess if bioethanol from sugarcane is a viable option to reduce energy-related GHG emissions.

Synergies between the mitigation of, and adaptation to, climate change in agriculture

SUMMARYThere is a very significant, cost effective greenhouse gas (GHG) mitigation potential in agriculture. The annual mitigation potential in agriculture is estimated to be 4200, 2600 and 1600 Mt CO2 equiv/yr at C prices of 100, 50 and 20 US$/t CO2 equiv, respectively. The value of GHG mitigated each year is equivalent to 420 000, 130 000 and 32 000 million US$/yr for C prices of 100, 50 and 20 US$/t CO2 equiv, respectively. From both the mitigation and economic perspectives, we cannot afford to miss out on this mitigation potential.The challenge of agriculture within the climate change context is two-fold, both to reduce emissions and to adapt to a changing and more variable climate. The primary aim of the mitigation options is to reduce emissions of methane or nitrous oxide or to increase soil carbon storage. All the mitigation options, therefore, affect the carbon and/or nitrogen cycle of the agroecosystem in some way. This often not only affects the GHG emissions but also the soil properties and nutrient cycling. Adaptation to increased variability of temperature and rainfall involves increasing the resilience of the production systems. This may be done by improving soil water holding capacities through adding crop residues and manure to arable soils or by adding diversity to the crop rotations.Though some mitigation measures may have negative impacts on the adaptive capacity of farming systems, most categories of adaptation options for climate change have positive impacts on mitigation. These include: (1) measures that reduce soil erosion, (2) measures that reduce leaching of nitrogen and phosphorus, (3) measures for conserving soil moisture, (4) increasing the diversity of crop rotations by choices of species or varieties, (5) modification of microclimate to reduce temperature extremes and provide shelter, (6) land use change involving abandonment or extensification of existing agricultural land, or avoidance of the cultivation of new land. These adaptation measures will in general, if properly applied, reduce GHG emissions, by improving nitrogen use efficiencies and improving soil carbon storage.There appears to be a large potential for synergies between mitigation and adaptation within agriculture. This needs to be incorporated into economic analyses of the mitigation costs. The inter-linkages between mitigation and adaptation are, however, not very well explored and further studies are warranted to better quantify short- and long-term effects on suitability for mitigation and adaptation to climate change. In order to realize the full potential for agriculture in a climate change context, new agricultural production systems need to be developed that integrate bioenergy and food and feed production systems. This may possibly be obtained with perennial crops having low-environmental impacts, and deliver feedstocks for biorefineries for the production of biofuels, biomaterials and feed for livestock.

Assessment of Technologies to Meet a Low Carbon Fuel Standard

California's low carbon fuel standard (LCFS) was designed to incentivize a diverse array of available strategies for reducing transportation greenhouse gas (GHG) emissions. It provides strong incentives for fuels with lower GHG emissions, while explicitly requiring a 10% reduction in California's transportation fuel GHG intensity by 2020. This paper investigates the potential for cost-effective GHG reductions from electrification and expanded use of biofuels. The analysis indicates that fuel providers could meetthe standard using a portfolio approach that employs both biofuels and electricity, which would reduce the risks and uncertainties associated with the progress of cellulosic and battery technologies, feedstock prices, land availability, and the sustainability of the various compliance approaches. Our analysis is based on the details of California's development of an LCFS; however, this research approach could be generalizable to a national U.S. standard and to similar programs in Europe and Canada.