Secondary GHG Effects

Definition

A Secondary GHG Effect is an unintended change caused by a GHG Project Activity in GHG Emissions, removals, or storage associated with a GHG source or sink.

Project activities often produce changes in GHG emissions aside from their primary effects—and these are termed secondary effects. As with Primary GHG Effects, these secondary effects are defined as a difference in GHG emissions between the GHG Baseline Scenario and the project activity. The baseline scenario used for estimating the secondary effects is the same as that identified for the related primary effect.

Secondary effects may be “positive” (e.g., involving a reduction in GHG emissions) or “negative” (e.g., involving an increase in GHG emissions). Secondary effects are typically small relative to a project activity’s Primary GHG Effects. In some cases, however, they may undermine or negate the primary effect. Therefore, it is wise to consider the type and magnitude of secondary effects before proceeding with rest of the GHG Project Protocol.

Classification

Secondary effects are classified into two categories:

• One-Time Effects: Changes in GHG emissions associated with the construction, installation, and establishment or the decommissioning and termination of the project activity.
• Upstream and Downstream Effects: Recurring changes in GHG emissions associated with inputs to the project activity (upstream) or products from the project activity (downstream), relative to baseline emissions.

One-Time Effects

One-time effects are identified by considering whether the project activity will require any practices, processes, or consumption or production of energy or materials during its establishment and termination that will cause a change in GHG emissions unrelated to the primary effect.

For some types of projects, large one-time effects may arise during construction or establishment from the transportation of equipment, or manufacturing and use of cement used in construction. During the decommissioning or termination phase, the one-time effects to consider may be associated with off-site waste disposal and dismantling equipment.

One-time effects during the establishment phase can also be large for some land-use projects. For example, reforestation and afforestation projects often require the clearing of vegetation to prepare a site for planting. This results in GHG emissions from the machinery used to clear the site, as well as the release of stored carbon from the cleared vegetation and disturbed soils.

Upstream and Downstream Effects

Upstream and downstream effects are identified by considering whether there are any inputs consumed or products/by-products produced by the project activity that will cause a change in GHG emissions unrelated to the primary effect during the project activity’s operating phase.

Estimation

Project developers should attempt to estimate the magnitude of secondary effects as a prelude to determining whether they are significant. Any method used to estimate secondary effects is prone to uncertainty. Because of this, the conservativeness prin- ciple should guide any effort to estimate their magnitude. For instance, it is advisable to use upper-bound estimates for project activity GHG emissions and lower-bound or zero estimates for baseline emissions. Use of a conservative estimate for baseline emissions is appropriate whenever it is difficult to determine the baseline scenario conditions related to a secondary effect. This is particularly relevant when the performance standard procedure is used to estimate baseline emissions for a project activity. In this case, it may be simplest to assume that the baseline emissions for secondary effects are zero, as the baseline scenario conditions may be ambiguous.

Following are some basic approaches for estimating the magnitude of secondary effects:

Default Data

Available default data or rough estimates often provide a reasonable basis for quantifying secondary effects, and are usually the most cost-effective route to take. Default or existing data are useful for all secondary effects that do not involve a market response, including one-time effects. Default data are also appropriate for estimating the magnitude of small secondary effects, which can in principle be aggregated together. In some cases, it may be possible to use default data from existing market assessments for upstream and downstream effects involving market responses.

Emission Factors

Many secondary effects can be estimated as the product of an emission rate and the level of input used or product produced that is related to the change in GHG emissions. This approach works well for upstream and downstream secondary effects. The key to this approach is to determine how input or product levels differ between the project activity and baseline scenario. For example, a change in methane emissions associated with the extraction of coal can be estimated as the product of an emission rate for methane (e.g., tonnes of CO2eq/tonnes of coal used) and the difference between the amount of coal used in the project activity and baseline scenario. If market responses are involved, however, it may sometimes be difficult to determine the change in quantities of inputs or products between the baseline scenario and the project activity. Estimating this change may require some kind of market assessment.

Market Assessment

A market assessment involves the economic modelling (e.g., equilibrium or econometric modelling) of the relevant market’s response to the project activity’s impact on supply or demand for an input or product. Many markets will not respond with a one-for-one substitution demand will not appreciably affect the behaviour of other actors in the market.

Examples

• Project activities that use fossil or biomass fuels to generate electricity, heat, or steam. Upstream effects may result from changes in the extraction of fossil fuels, the harvest of biomass, and the transportation of either type of fuel—e.g., changes in the release of methane (CH₄) during coal mining, the release of CO₂ from fuel combustion during harvesting, and the release of CO₂ from transporting coal or biomass
• Project activities that cause a change in the use of materials or products that give rise to GHG emissions as a result of physical or chemical processing during their manufacture, use, or disposal.
• Project activities that cause a change in the use of materials or products whose application gives rise to GHG emissions—e.g., changes in nitrous oxide (N₂O) emissions associated with the application of nitrogen fertilizer; changes in HFC leakage from refrigeration equipment, or changes in the use of lime in sulphur dioxide scrubbers in a coal fired boiler.
• Project activities that involve the transportation of materials, employees, products, and waste. Changes in GHG emissions may arise from changes in the combustion of fuels in vehicles, trains, ships, and aircraft.
• Project activities that affect levels of fugitive or vented emissions. For example, a project activity may incidentally cause changes in GHG emissions from leaking joints, seals, packing, and gaskets; CH₄ emissions vented from coal mines; or CH₄ leaks from gas transport and storage.
• Project activities that cause changes in GHG emissions from disposed waste—e.g., changes in CH₄ emissions from landfilled waste, even if these changes occur much later than the implementation of the project activity.

Market Responses

Some upstream and downstream effects may involve market responses to the changes in supply and/or demand for project activity inputs or products. Only significant secondary effects, however, need to be monitored and quantified under the GHG Project Protocol. Whether a secondary effect is considered significant depends on its magnitude relative to its associated primary effect and on circumstances surrounding the associated project activity.

Issues and Challenges

• One-Time Effects concern secondary effects on emissions. Other unintended effects are outside the GHG protocol. See e.g. Do No Significant Harm Principle