Methodologies for calculating emissions from low carbon fuels

Emissions of carbon dioxide and other greenhouse gases are considered to be primarily responsible for the global warming that has been experienced in recent decades. This global warming translates into climate change, the consequences of which can have a major impact on human beings in areas such as flooding, extreme temperatures or even problems in food production and supply.

In order to reduce the impact of climate change, most governments worldwide are implementing measures to reduce greenhouse gas emissions to mitigate global warming. These measures are mainly focused on the substitution of fossil fuels to cover our needs in the energy, transportation and industrial sectors.

This substitution must be carried out using alternatives whose emissions are lower than those of traditional fuels. Among the main options are renewable energies, especially solar and wind energy, as well as the use of biomass.

Hydrogen, without being an energy source per se (with the possible exception of natural hydrogen), is a fundamental energy vector for reducing emissions in those applications where the aforementioned energies do not have a direct application or represent a challenge (for example, in heavy transport).

Moreover, the use of hydrogen as a raw material in industrial processes is currently associated with a non-negligible carbon footprint (10-12 kg CO2/kg H2) due to the use of fossil fuels in its production (mainly through the reforming of natural gas), so that production through alternative technologies with lower emissions (e.g. hydrogen from electrolysis powered by renewable energy) will have a great impact on reducing greenhouse gas emissions.

The use of alternative technology with the aim of reducing carbon emissions represents a challenge and an impact on the different sectors in which these changes will take place. For example, the use of electric vehicles implies the development of a recharging infrastructure and refueling times that are much longer than what we are used to. That is why, before replacing a traditional technology with a possible alternative, it is necessary to ensure that this alternative will represent an improvement in terms of emissions.

This aspect becomes even more important when governments provide economic support for certain technologies in the hope of achieving decarbonisation targets. In this case, it is necessary to certify that public money is being spent on those technologies that will have the greatest impact on reducing emissions.

For this reason, methodologies are being developed to calculate the emissions associated with the use of each technology. This calculation not only focuses on the production process, but also includes the emissions associated with the entire value chain, from the extraction of raw materials for the production of equipment to the management of waste at the end of its useful life. This type of methodology is based on Life Cycle Assessment (LCA).

Life Cycle Assessment

Life cycle analysis is a tool for estimating and evaluating the environmental impacts that a product or service may have during all stages of its life.

The life cycle analysis methodology was initially proposed in the 1960s. It focuses on identifying and describing the stages of the life cycle of products, from the extraction of raw materials, production, distribution and use of the final product to its possible reuse, recycling or disposal.

This methodology identifies not only carbon emissions but also many other environmental impacts such as acidification, ecotoxicity or resource consumption.

When applying this methodology, international references such as ISO standards can be used:

• ISO 14040. Environmental Management. Life Cycle Assessment. Principles and framework.

• ISO 14044. Environmental Management. Life Cycle Assessment. Requirements and guidelines.

In addition, the DG Joint Research Centre of the European Commission has developed an extensive manual for the execution of life cycle analysis known as the ILCD Handbook, which consists of different volumes detailing the methodologies, environmental impacts and data processing to be followed when carrying out an LCA.

As shown in Figure 2, the LCA consists of a series of fundamental stages:

• Definition of the objective of the LCA.

• Definition of the scope of the LCA: The object of the LCA (product or system, for example) is identified and defined in detail.

• Inventory analysis: The materials and resources used in the different stages are identified, as well as the impact associated with them.

• Impact analysis: Calculation of the impact based on the information obtained during the previous stage.

• Interpretation: In which the main conclusions are obtained from the results obtained.

The LCA process is an iterative process in which the results obtained at one stage may make it necessary to return to earlier stages to refine or revise the decisions made.  A key aspect in conducting an LCA is the information relating to the materials and resources used, as well as the associated environmental impact. With regard to the latter, there are a variety of databases that can be used to identify such impacts. However, the impact identified for a particular raw material or resource may vary between databases. This difference may be due to different calculation methods or to the location of the raw material or product. For example, the extraction of a mineral may have a greater impact depending on where it is extracted.

Another important aspect when calculating emissions from a given product is the distribution of these emissions among the different co-products produced in the process. This is known as allocation. For example, during hydrogen production, steam may also be produced (in the case of natural gas reforming), which can be used in other processes or even sold to an external customer.

The allocation of total emissions can be done on the basis of different parameters. This can be done, for example, on the basis of the energy content of the products, or on the basis of the weight or volume of the products. The decision on the basis of which emissions are allocated can have a considerable impact on the emissions associated with a given product.

The LCA methodology described is known as “attributional”. Another alternative is the “consequential” LCA, which analyses the impact that may be generated as a consequence of a change in the demand of the functional unit. Consequential LCA therefore attempts to quantify the changes caused by a decision or intervention in a system.

In the specific case of calculating greenhouse gas emissions, there is the ISO 14067 standard. PRODUCT CARBON FOOTPRINT which is based on the standards mentioned above and defines in general terms the methodology to be applied.

Life cycle analysis applied to hydrogen production

Due to the relevance of hydrogen for achieving decarbonisation objectives, several methodologies for calculating carbon emissions associated with hydrogen production are being implemented internationally or are in the process of being developed.

These methodologies are based on life cycle analysis. Despite starting from the same basis, the methodologies developed are not identical, which can lead to different carbon footprints for the same production system depending on the methodology applied.

As mentioned above, these calculation methodologies can be used by governments or certification bodies to identify the carbon emissions associated with a certain amount of hydrogen produced through a given technology. This quantification will serve to classify such hydrogen within a specific category (renewable hydrogen, for example) and such categorisation will allow to obtain, or not, certain allowances or tax benefits.

The application of different methodologies to obtain different results can be a challenge for international hydrogen trade. A given quantity of hydrogen may have a carbon footprint under a methodology applicable in one part of the world (the USA, for example) that may differ from that obtained in another part of the world (Europe, for example). This, together with the different requirements regarding emissions that can be found in different international legislations, can mean that a hydrogen considered as renewable, or at least with the possibility of receiving some kind of fiscal support in one country or region, may not have the same status and/or support in other countries or regions.

As mentioned above, there are a large number of methodologies for calculating emissions in hydrogen production. For example, the European Union’s second delegated act establishes the methodology for calculating the reduction in greenhouse gas emissions achieved by using renewable fuels of non-biological origin (including hydrogen) and recycled carbon fuels. The methodology takes into account the full life cycle of the fuels to calculate the emissions they produce and the emissions reductions they imply.

On the other hand, in the USA, subsidies under the Inflation Reduction Act (IRA) are based on emissions calculated through the GREET model. This model has been developed by the Argonne National Laboratory to evaluate the energy consumption, emissions and environmental impact of technologies in order to assist R&D programs as well as various standards and regulations.

Globally, GH2 (Green Hydrogen Organisation) has developed a standard that accredits and certifies hydrogen production, allowing hydrogen producers to label their product as green hydrogen.

In addition, the International Standard Organisation (ISO) is developing a standard for hydrogen production calculation methodology, ISO 19870-1 – Emissions associated with the production of hydrogen up to production gate. This is a standard that in future developments will also include conditioning and transport to the point of consumption.

The following section describes the main existing methodologies in a little more detail and with a focus on the main differences.

Scond Delegated Act

This methodology has been developed in the framework of the European Renewable Energy Directive (Directive (EU) 2018/2001) in order to identify the emissions associated with renewable fuels of non-biological origin (RFNBO).

According to this methodology, greenhouse gas emissions from hydrogen production will be calculated as follows:

where:

E = total emissions from fuel use (gCO2eq-/-MJ of fuel)

e i = elastic e i + rigid e i – e use-ac: emissions from input supply (gCO2eq/MJ of fuel)

e i elastic = emissions from elastic inputs (gCO2eq/MJ of fuel)

e i rigid = emissions from rigid inputs (gCO2eq/MJ of fuel)

e use-ac = emissions from current use or destination of inputs (gCO2eq/MJ of fuel)

e p = emissions from transformation (gCO2eq/MJ of fuel)

e td = emissions from transport and distribution (gCO2eq/MJ of fuel)

e u = emissions from fuel combustion during final use (gCO2eq/MJ of fuel)

e ccs = emission reductions from carbon capture and geological storage (gCO2eq/MJ of fuel)

This methodology does not take into account emissions from the manufacture of machinery and equipment. In addition, the concepts of elastic and rigid inputs, which belong to consequential LCA approaches, are included.

Rigid inputs are those that cannot be supplied in greater quantities to meet additional demand. For example, this methodology considers all inputs that are considered a carbon source for the production of recycled carbon fuels to be rigid, as are final products obtained in a fixed proportion in a process taking place in the same industrial complex and representing less than 10% of the economic value of production. If they represent 10 % of the economic value or more, they are considered to be elastic.

In principle, elastic inputs are those that can be supplied in larger quantities to meet additional demand. Petroleum products from refineries fall into this category because refineries can change the proportion of products obtained.

Emissions from rigid inputs will include emissions resulting from diverting these inputs from a previous or alternative use. These emissions shall take into account the loss of production of electricity, heat or products that were previously generated using the input, as well as any emissions due to treatment and transport.

This methodology attributes a value of zero greenhouse gas emissions to electricity that is considered fully renewable under Article 27(3) of Directive (EU) 2018/2001. This includes the concept of additionality, i.e. that the renewable energy production plant comes into operation after or at the same time as the installation producing the hydrogen.

In the case of installations fed from the electricity grid, emissions may also be considered zero if the number of hours of operation at full load is equal to or less than the number of hours in which the marginal electricity price has been set by installations producing renewable electricity or by nuclear power plants.

The methodology includes a database reflecting emissions associated with certain raw materials and resources. If information on other inputs is needed, the methodology indicates that it can be extracted from the latest version of the JEC-WTW report, from the ECOINVENT database, from official sources such as the IPCC, IEA or the Government, from other revised sources such as the E3 or GEMIS databases, or from revised publications.

This database also identifies upstream emissions from a range of fuels. These emissions are associated with the extraction, transportation and preparation of fuels prior to consumption.

GREET model

This methodology has different versions depending on its field of application. The Argonne R&D GREET Model is used to evaluate the energy use and emissions of technologies related to the transport and energy sector to assess progress in the R&D field. Moreover, the ICAO-GREET is used to estimate and verify emissions associated with sustainable aviation fuels (SAF).

The CA-GREET4.0 model is a version adapted to reflect California-specific fuel scenarios for application in the California Low-Carbon standard.

For application in the Inflation Reduction Act (IRA) the GREET has been adapted to calculate emissions associated with SAF (40BSAF-GREET) and to calculate emissions associated with clean hydrogen production (45VH2-GREET).

The 45VH2-GREET tool is designed to calculate the emissions associated with hydrogen production, including the emissions associated with the resources required for hydrogen production and further processing (e.g., carbon capture) as shown in the example shown in Figure 3.

This tool incorporates a series of data that cannot be modified by the user, especially in those parameters where it is difficult to verify the reliability of the information provided by the hydrogen producer. Examples of these parameters are the carbon footprint of the electricity used (see Figure 4) or the upstream emissions associated with methane leakage.

As mentioned at the beginning, this tool is developed to support the requirements of the Inflation Reduction Act, so it also incorporates aspects such as additionality and geographical and temporal correlation when considering the electrical energy used as renewable.

The 45VH2-GREET model’s emissions calculation is based on the production of one kilogram of pure (100%) hydrogen at a pressure of 20 bar, even though this is not the condition of the hydrogen produced by the user. The tool integrates a functionality that allows recalculating the emissions of the hydrogen produced (99% and 10 bar, for example) to the emissions that the same hydrogen would have under the conditions on which the 45VH2-GREET is based (100% purity and 20 bar), considering the excess or deficit of electrical energy necessary to reach those values (purification and compression processes).

In addition, the model assumes that all carbon impurities in the hydrogen will be converted to CO2 by the end user. As for the impact of greenhouse gases, this model is based on the values indicated by the IPCC in its AR5 report, in the time frame of 100 years.

The tool incorporates different technologies for hydrogen production, which can use renewable (including biomass), fossil or nuclear energy sources. For each technology, the tool requires specific information about the feedstock and resources used, as well as the characteristics of the hydrogen produced and the treatment of other by-products (e.g., carbon capture).

The 45VH2-GREET tool only accepts steam, oxygen and/or nitrogen as co-products to be considered when allocating emissions. In the case of steam, it does not allow the user to introduce amounts of steam that exceed 17.6% of the total energy content of the steam and hydrogen produced, according to the expected yields of the reforming technology. In addition, if the system incorporates carbon capture and storage, the steam cannot be considered as a co-product (since it is assumed that it would be used for carbon capture and storage).

Green Hydrogen Standard

This is a tool developed by the non-profit Green Hydrogen Organisation (GH2) to certify the renewable origin of the hydrogen produced, which the organisation identifies as green hydrogen. For GH2, green hydrogen is hydrogen produced by electrolysis of water using 100% (or close to 100%) renewable energy, with greenhouse gas emissions close to zero (<1 kg CO2/kg H2).

The methodology used by this standard is that developed by the International Partnership for Hydrogen and Fuel Cells in the Economy (IPHE), focusing on three types of electrolyser technologies (Alkaline, PEM and SOEC) and identifying the supply of 1 kg of hydrogen at 3 MPa and greater than 99% purity as the functional unit. The calculation of emissions in this standard is limited to emissions related to the energy supply necessary for the different processes (electrolysis, compression, purification and/or drying). This standard does not include upstream emissions in the calculation of the carbon footprint, as well as those related to conditioning and transport to the end user, although in both cases it is recommended that they be measured. An outline of the processes included in this standard is shown in Figure 6.

This standard, in addition to considering the traditional greenhouse gases (CO2, CH4, N2O) will include in future versions, the indirect impact of hydrogen leakage on the greenhouse effect.

Regarding the database, this standard does not provide any information on the values to be used when identifying emissions associated with raw materials and energies, leaving it up to the user to identify these values. It is necessary, in accordance with the LCA methodology, to provide a detailed reference of the values used, identifying their level of uncertainty and performing sensitivity analysis if deemed necessary, also in accordance with the LCA methodology.

Conclusions

Hydrogen is identified as a fundamental tool for achieving decarbonisation objectives. However, it is necessary to use tools to verify that its use represents a benefit compared to conventional technologies based on fossil fuels.

For this reason, the development and application of tools for calculating these emissions based on the life cycle analysis methodology is spreading, which allow understanding all the emissions associated with producing and distributing a certain amount of hydrogen, both due to the energy consumed and other resources necessary to carry out such production and distribution to the end user.

These tools are also being used in the framework of regulations that identify the minimum requirements for hydrogen to have a certain consideration, whether it is renewable, clean or green, for example, granting tax advantages to such hydrogen.

However, these tools are lacking a sufficient degree of compatibility between them, either by not using the same methodology or by integrating databases with emissions values that differ between tools. This difference can be a challenge, since for the same hydrogen production process, different emission values can be obtained depending on the tool. As mentioned above, the associated emissions value will be the one that defines the type of hydrogen and the fiscal support it can obtain. Moreover, this difference in emission calculation tools is especially critical for those producers who intend to sell hydrogen in different markets with different emission verification tools.

SynerHy can help you in the use and application of these tools thanks to our extensive experience, both in their analysis and their development.