(139d) 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

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.