Beneficial Uses of CO2: Preliminary Framework for Quantifying Impacts

Beneficial Uses of CO₂: Preliminary Framework for Quantifying Impacts

We present a preliminary framework for quantifying the impact of existing or potential beneficial processes using CO₂.  A beneficial use is an application which creates a market for CO₂ producers and value to the end user.  The quantities of CO₂ used in beneficial use applications may be small compared to the potential for CO₂ mitigation from geologic carbon capture and storage (CCS).  Compared to geologic storage, using CO₂ for beneficial purposes may be more valuable (e.g., hydrocarbon resource recovery), or may be perceived as having a lower risk (e.g., applications where carbon dioxide is consumed).  Income from high-value products produced from the beneficial use of a slipstream of captured CO₂ could offset a portion of the capital and operating costs for CCS.  The higher-value potential and lower-risk perception may also accelerate the development of CO₂ pipeline networks, and the deployment of novel technologies, in turn, enhancing prospects for geologic CCS.  For instance, CO₂ used for enhanced oil recovery may also be injected into suitable saline formations adjacent to the oil reservoir, thereby reducing the need for additional infrastructure (wells, pipelines, equipment) at such locations.  In other cases, if the produced CO₂ would be used within an industrial complex, only small modifications to existing pipeline networks may be needed.  We recognize that not all CO₂-use processes are at similar levels of technology readiness.  Development of tools to assess impacts is nevertheless helpful because it provides a baseline for comparison of multiple CO₂ use processes, collates current and potential beneficial impacts, and identifies game-changing scenarios which might significantly benefit a CO₂-use process.

The framework was applied to three categories of CO₂ uses:

      i.         CO₂-enhanced hydrocarbon recovery: CO₂-enhanced oil recovery (CO₂-EOR), enhanced coal bed methane production (ECBM), enhanced gas recovery (EGR), enhanced gas hydrate recovery (EGHR), hydrocarbon recovery from oil shale, and the fracturing of reservoirs to increase oil/gas recovery.

    ii.         Non-consumptive or CO₂-reuse applications: Processes where CO₂ is not consumed directly, but re-used or used only once.  Examples include the use of CO₂ for desalination, and as a solvent or a working fluid.

   iii.         Consumptive uses: Applications leading to the formation of minerals, or long-lived compounds from CO₂ leading to net-carbon sequestration by ‘locking-up' carbon, e.g., production of carbonate minerals from CO₂.

The framework for quantifying impacts is based on four elements:

      i.         Quantity of CO₂ mitigated in the process or application (annual (metric tonnes [T] CO_2eq/y) or cumulative (T CO₂)),

    ii.         Unit value (beneficial impact) or cost (measured typically as $/T CO_2eq),

   iii.         Energy consumed by the application, or net-energy saved by implementing this technology  (net-CO₂ savings from the technology) and,

   iv.         Market potential of primary CO₂ use and any by-products.

The first metric, quantity of CO₂ mitigated, reflects direct-use and indirect-use/emission of CO₂ in the process, subject to the availability of sufficient information.  Processes using CO₂ from flue gas and other dilute sources have less indirect-CO₂ emissions because they avoid the need for energy-intensive CO₂ separation steps.  Another metric of relevance is the net-CO₂ mitigation, closely related to the amount of energy consumed in the process (metric #3).  Typical examples are the use of electrical, thermal, or chemical energy in applications which chemically react, compress, or use CO₂.  The net-CO₂ used in the process, or mitigated per unit of process output (product) would therefore be the gross-amount of CO₂ used per unit of product, less the amount of CO₂ emitted during the process per unit of product.  Because (fossil) energy use and CO₂ emissions are correlated, emissions from the CO₂-use process can also be deduced by energy consumption, energy required for capture and/or disposal, energy penalty or energy gain, and the energy use avoided.

The costs of CO₂ separation, compression, and delivery may be offset by a variety of methods under some carbon management regimes, but in the absence of a specific regime, they must be accounted for to estimate overall economic impacts of beneficial use applications or processes.  Economic impacts are best estimated with detailed lifecycle cost-benefit analyses, which require high-levels of detail about individual processes..  Instead, in this framework, a measure of value, “nominal net-positive benefit”, is defined as the value realized from the use of CO₂ less the costs of raw materials involved in the CO₂-use process.  This approach does not account directly for the capital and processing costs of CO₂ utilization, which are process-specific and highly uncertain in some cases.  The costs of CO₂ capture and compression are aggregated as the cost of high-pressure, pure CO₂ (assumed to be 40 $/T).  Relative comparisons of net benefits from various beneficial uses are more relevant than the absolute values themselves.  Positive benefits are indicated by negative costs, and vice versa.

Table 1 - Metric Summary

CO2 Mitigation	(1) Amount of CO2 reduced (total : direct + indirect)
	(1.1) Amount of captured CO2 utilized (direct reduction)
	(1.2) Amount of CO2 consumed
	(1.3) Is capture an intrinsic part of the process?
Benefits	(2) Cost of CO2 reduction/ tonne (total system basis)
	(2.1) Cost of CO2 capture and processing
	(2.2) Value of by-products
Energy Consumption	(3) Energy penalty/ gain for total system
	(3.1) Energy required for capture and disposal
	(3.2) Energy penalty/ gain for byproduct process
	(3.3) Energy use avoided
Market Potential	(4) Market size (potential tonnage removed from atmosphere)
	(4.1) CO2 subjected to capture and storage
	(4.2) CO2 sold to commercial markets for consumption or resource recovery
	(4.3) Market size of by-products
	(Nominal Benefit (Negative cost)) x Market size

The fourth metric in the framework is the market potential of CO₂-use applications.  The market size sets an upper limit to the amount of CO₂ that could be potentially used.  For example, the current or projected levels of demand will limit the amounts of CO₂ that could be potentially converted to fuels, plastics, and carbonates.  In certain cases, the market size of by-products may be larger than that of the primary-use application itself.

Examples of application of these metrics to hydrocarbon recovery applications, consumptive uses and non-consumptive uses of CO₂ will be discussed in the presentation.