LCA projects can now add a processing stage at the hub and easily include pre-defined processing steps before the product moves downstream. Processing steps currently cover food processing (75 unit processes) and yarn/fabric/garment production (21 unit processes)
GHG inventory projects can automatically upload hybrid activity data from a spreadsheet, covering: fuel and electricity use, purchased goods and services, waste management, freight transport, warehousing, energy used in processing and use phase, and employee travel/commuting.
CarbonScopeData API for climate/carbon app developers: This is a RESTful web service that provides access to both process LCI and environmentally extended input-output LCI data.
Process LCI data
Electricity emission factors for ALL countries, except the US, have been updated using the latest electricity statistics from the IEA. US emission factors continue to be based on the latest eGRID data.
Cradle-to-gate LCI data for 80 different plastics and related chemicals has been updated using the latest eco-profiles from PlasticsEurope.
Unit process data for yarn, fabric and garment production has been added to the database. There are 21 unit processes in this category with the ability to distinguish energy use in yarn and fabric production based on the type of input fiber.
Unit process data for food processing has been updated and enhanced and now totals 75 unit processes covering a wide range of processing and cooking steps.
We are seeing a surge of interest in life cycle assessments (LCAs) for determining the carbon footprints of food products. In many food LCAs, attention turns rather quickly to the agricultural practices used to produce the ingredients. This is especially the case with producers of processed food products who source ingredients grown using organic and/or regenerative methods. We summarize here what is in our soil model as implemented in FoodCarbonScope and CarbonScopeData, how we model soil dynamics and what the standards say about all this.
The diagram above captures the flow of key inputs into the soil and the resulting emissions of greenhouse gases (GHGs) as well as sequestration of soil organic carbon. The inputs of interest are synthetic fertilizers, organic fertilizers and soil amendments, and crop residues. The soil model basically tracks, to a first-order approximation, what happens to the nitrogen and carbon in these various inputs. The GHGs that are released as a result of these inputs, as well as due to land management practices and climatic conditions, are nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4).
How we model soil dynamics
Changes in soil organic carbon
We use the IPCC tier 1 parameters (see discussion in the last section) to estimate changes to soil organic carbon (SOC) stocks in croplands. These parameters are a function of land management practices (tillage method, carbon inputs to soil), climate zone, moisture regime, and soil type. The default time period for stock changes is nominally 20 years and management practice is assumed to influence stocks to a depth of 30 cm. Soil carbon is considered to be in steady state until there is a significant land-use change (such as a conversion from grassland to cropland) or management change (such as a conversion from conventional cropland to organic cropland) that changes the soil carbon stocks.
When such a change occurs, the soil carbon is assumed to reach steady state again after 20 years under the new land-use or management practice. During this 20-year transition period, soil carbon may be increasing or decreasing each year as illustrated below, thus increasing or decreasing the total greenhouse gas emissions and the product carbon footprint during that period. When soil carbon is in steady state, it does not contribute to net emissions in agricultural systems.
Regarding the question of why a steady-state organic farming system does not get credit for the potentially higher level of carbon (relative to a conventional farming system) already accumulated in the soil: The addition of organic matter balances the carbon that is naturally oxidized away from the top layers of the soil, so in an ideal steady-state system, the SOC level remains constant and the net change in soil carbon is zero. LCA models account for this net change and a production system can take credit in the years that this net change > 0. Likewise, if we allowed the organic system to degrade by not adding sufficient organic matter to the soil for a few years, it would result in a new transition with net change < 0, resulting in a higher carbon footprint for those years. So maintaining a steady-state organic system avoids this higher carbon footprint — and that in a nutshell is the benefit of continuously adding organic matter to the soil. That benefit is already reflected in the stable carbon footprint of a steady-state organic system.
The 20-year transition period itself is not a critical parameter. Our tools allow the user to set this to any reasonable value. The more important issue is the magnitude of changes to the SOC stocks over the transition period. There can be wide variability and crop specificity in field measurements of soil carbon stocks, and the tier 1 parameters provide useful estimates of typical SOC changes while avoiding the complexity and data collection effort associated with tier 2/3 models.
Nitrous oxide emissions due to nitrogen inputs
Synthetic nitrogen fertilizers (nitrate, ammonia, ammonium or urea) and organic nitrogen sources (compost, manure or crop residues) produce direct N2O emissions from the soil through the nitrification-denitrification process mediated by soil bacteria. In addition, indirect N2O emissions result from the volatilization and redeposition of NH3/NOx, and through leaching and runoff of nitrogen.
We calculate both direct and indirect N2O emissions based on the amounts of synthetic and various organic nitrogen sources added to the soil each year, as well as due to nitrogen from crop residues and distinguishing between typical agricultural soils and flooded rice fields. We also make an adjustment for legumes to account for the excess ammonium that may leak from nitrogen-fixing root nodules and ultimately escape to the atmosphere as N2O.
Carbon dioxide emissions due to lime and urea
CO2 is released directly due to the application of lime and urea to agricultural soils. Liming is used to reduce soil acidity and improve plant growth. When carbonates such as limestone (CaCO3) are added to soils, they dissolve and release bicarbonate (HCO3-) which evolves into CO2 and water. When urea is applied as a fertilizer, it releases bicarbonate which again evolves into CO2 and water. We calculate these CO2 emissions based directly on the amounts of lime and urea applied each year to a given land area.
Methane emissions from rice fields
Anaerobic decomposition of organic material in flooded rice fields produces CH4. We calculate the annual amount of CH4 emitted from a given area of rice as a function of the crop growth period (measured in days), irrigation method (such as continuously or intermittently flooded), and organic and inorganic soil amendments (such as straw, compost and/or manure).
What the standards say
IPCC guidelines
The IPCC guidelines for national greenhouse gas inventories provide the most detailed and standardized guidance available for calculating soil carbon emissions and sequestration, N2O emissions from soils, and CH4 emissions from soils. Given that the current product carbon footprint standards do not provide detailed guidance on these topics but defer to IPCC in general, our methodology for modeling soil dynamics is based almost entirely on the IPCC guidelines.
There are three tiers of methodology in the IPCC guidelines. We have found the tier 1 methods to be the most appropriate for LCA models used to compute product carbon footprints. Given the time and cost constraints in most LCA projects, as well as the sheer difficulty involved in obtaining country-specific data or field measurements, we use tier 1 methods as a practical default unless higher tier data are readily available.
Here is a brief description of the three tiers:
Tier 1 methods are designed to be the simplest to use, for which equations and default parameter values (e.g., emission and stock change factors) are provided by IPCC. Country-specific activity data are needed.
Tier 2 can use the same methodological approach as Tier 1 but applies emission and stock change factors that are based on country- or region-specific data.
At Tier 3, higher order methods are used, including comprehensive field sampling repeated at regular time intervals and/or GIS-based systems of age, class/production data, soils data, and land-use and management activity data, integrating several types of monitoring.
Product carbon footprint standards
Neither of the two leading product carbon footprint standards, PAS-2050 and the GHG Protocol Product Standard, requires soil carbon changes (due to changes in management practices such as tillage) to be included in the carbon footprint of agricultural products. The default is to exclude it, but both standards provide for ways to include it (in the case PAS 2050, it can be included in accordance with the standard’s supplementary requirements). Both standards do require direct land use change (such as conversion from grassland to cropland) to be included per IPCC guidelines, but indirect land use change is not included in the carbon footprints. Our methodology is consistent with both standards, and we do include the effects of both land management practices and direct land use changes.
PAS 2050 requires non-CO2 emissions (N2O, CH4) from soils to be assessed using the highest tier approach set out in the IPCC guidelines or the highest tier approach employed in the country in which the emissions are produced. The Product Standard does not provide specific guidance on this. Our methodology takes a compromise position here and defaults to using the IPCC tier 1 parameters to calculate these soil emissions.
Carbon registries
The methodology described here generally aligns with the principles developed by carbon registries (for example, the Climate Action Reserve’s Soil Enrichment Protocol) for allocating carbon credits based on soil carbon sequestration.
We partnered
with a US-based producer of organic, plant-based frozen desserts to test drive our
hybrid methodology for compiling a corporate greenhouse
gas (GHG) inventory. This is the partner company’s first GHG inventory,
intended to establish a baseline for annual emissions and a basis for
potentially offsetting those emissions.
The hybrid
methodology combines two kinds of life-cycle inventory data to quickly and
efficiently produce a GHG inventory using CarbonScope:
All of the emissions in scope 1 (direct
fuel combustion) and scope 2 (purchased electricity) are modeled using
our process LCI (PLCI) database,
which converts physical quantities of energy use into GHG emissions.
The company is classified as a small company (less than
100 employees and/or less than $50M in annual revenue). The company outsources
its product manufacturing to two co-packers both of whom are outside of the
company’s organizational boundary on an operational control basis, so the
entirety of the co-packer emissions will be categorized as scope 3.
Activity data
The company provided
activity data for this baseline inventory based on their operations in 2019,
using our standard data template for hybrid GHG inventories. The actual data is
confidential, but here is an example of what the input
data might look like for a hypothetical company. The activity data typically
includes:
Fuel and electricity consumed in
company operations – in physical units such as kWh, gallons, etc.
Goods and services purchased
(inflows) – in 2019 US dollars excluding taxes
Waste management services
purchased– in 2019 US dollars excluding taxes
Freight transport services
purchased– in 2019 US dollars excluding taxes
Warehousing and storage services
purchased– in 2019 US dollars excluding taxes
Energy used in processing and
use of sold products– in physical units such as kWh, gallons, etc.
Employee travel and commuting—in
passenger miles or km
The larger of the two
co-packers was able to provide their detailed activity data separately. The
smaller co-packer was modeled as a supplier providing frozen dessert
manufacturing services within the company’s purchased goods and services.
The company sources 100%
of its electricity from renewable sources supplied by the local utility. The
larger co-packer produces about 3.2% of its electricity using on-site solar,
with the remainder sourced from the local grid.
Some of the plant-based ingredients
used in the dessert products are imported, which are modeled using domestic
production as proxy by assuming that imported commodities have the same input
structure and the same production characteristics as comparable products of
equal value produced domestically (see this methodology note). While all of the purchased ingredients are organically
produced, the inventory uses emission factors for industry sectors as a whole
without distinguishing between conventional and organic production. This can be
justified by the fact that organic farming does not necessarily have lower
carbon footprints than conventional farming when systems are in steady state.
Inventory results
The results of the GHG inventory analysis show that the company’s operations from all three emission scopes amount to 8387 metric tonnes of CO2e for the year 2019. The table and chart below show a detailed breakdown (units: Carbon in Kg CO2e; Energy in MJ; Water in L).
A sensitivity analysis shows that the natural gas used by the larger co-packer is by far the largest contributor to the corporate GHG emissions, accounting for 49% of the total emissions and reported under scope 3.3. The next four contributors are the ingredients sourced by the larger co-packer (16.6% of total emissions; scope 3.1), manufacturing services provided by the second co-packer (9% of total emissions; scope 3.1), truck transport services used to ship finished products (7.6% of total emissions; scope 3.9), and cardboard containers used to ship finished products (3.8% of total emissions; scope 3.1). Overall, scope 3 emissions account for over 99% of the total emissions and 72% of the total emissions are attributable to the larger co-packer.
For a hypothetical
company with revenue at the midpoint of the range for the company size, the GHG emissions intensity is 0.36 Kg CO2e
per dollar of revenue. This intensity is less than 50% of industry average for
the ice cream and frozen dessert sector in the US.
Effort
We said at the outset
that our hybrid methodology provides for a quick and efficient way to compile a
corporate GHG inventory. Here is a quick
accounting of the time and effort that went into generating the inventory:
About 2.5 weeks of work by the
company’s sustainability team to collect activity data from within the company
and from the co-packers.
A few hours to automatically
import the data into CarbonScope, generate results, and review/interpret the
results.
With a baseline GHG
emissions inventory established using a simple and well-understood methodology,
annual updates to the inventory are expected to take less time/effort and turn
into a routine accounting task.
Think before you drink: The carbon footprints of four different hydration options
Susan Cholette and Hoa Nguyen
Project summary
Hydration
is a necessity, and the growing consumer shift away from soft drinks towards
water should please dentists and physicians alike. However, as worldwide demand has surpassed
half a trillion bottles per year, single use plastic bottles are not the healthiest
choice for the planet. We compare
several scenarios for quenching thirst on the go, and show how our purchasing
habits can make a substantive impact.
Systems modeled in this study
We evaluate
four different ways to provide a thirsty Bay Area consumer a half-liter of
water: imported bottled water, more locally
sourced water bottled in both virgin and 100% recycled PET bottles, and a
reusable container that can be refilled as needed.
The following figures illustrate the supply chains for a 500ml bottle of Evian, imported from Switzerland, and Arrowhead™, which sources from Californian springs. According to their website all of Arrowhead™’s individually sized bottles sold in California are currently comprised of a 50/50 mix of virgin and recycled PET, but they indicate their bottle design can support use of 100% recycled content and will eventually. Some other drink companies, such as Snapple™ have recently re-designed their bottles to use 100% recycled content. We consider both extremes for recycled content- 0% and 100%- to illustrate the relative impact that recycling has, and we assume that the recycled PET is sourced from the same location as virgin PET.
Figure 1: System diagram for a 500ml bottle of Arrowhead™ water
Figure 2: System Diagram for a 500ml bottle of Evian™ water
While consumers have many options for reusable containers, we select a Nalgene™ bottle to keep within the same family of materials, as it is made of Tritan™, a popular form of PETG plastic. Unlike the prior three scenarios, where the functional unit is a half liter bottle of water, the functional unit is just the Nalgene™ bottle itself, as it is purchased empty and then filled at home or at a drinking fountain, as shown in Figure 3. We assume that no additional filtration or treatment is used.
Figure 3: System diagram for a Nalgene™ reusable container
All four
scenarios share the same system boundary,
cradle-to-grave, where we assume that the bottles are trucked to landfill once
discarded, as only about 30% of plastic containers are recycled in the US.
LCA tool and LCI database
We used our carbon modeling tool, CarbonScope, to conduct the LCAs in this project. The life-cycle inventory (LCI) database underlying the analysis is CarbonScopeData.
Results
The three life-cycle impact categories that can be quantified are embodied carbon (kg CO2e), embodied energy (MJ) and embodied water (L), but to keep the comparisons simple, we report only embodied carbon. Other studies published elsewhere discuss the additional problem of landfill usage and pollution from bottles that escape proper disposal.
Figure 4 shows the relative impacts of each of the bottles and the contribution for each stage towards embodied carbon. The domestically sourced water bottled in 100% recycled PET has the lowest footprint, a 30% reduction over the virgin PET bottle. Imported water has almost three times the footprint, thanks to the international transportation required. Figure 4 also shows that distance trumps recycled content: even if we were to buy an imported brand bottled in 100% recycled materials, it is clear that it would have more embodied carbon than the domestic water bottled in virgin PET. The reusable container has the most embodied carbon due to its greater weight, more energy-intensive material, and the need to transport it across the country.
Figure 4: Embodied carbon associated with a single use of each of the four bottles
Of course, it would be silly to purchase a reusable container for one time use. Figure 5 illustrates the how cumulative carbon footprint increases with the number of uses. We include the .001 kg CO2e associated with pumping and treating tap water, a miniscule impact that effectively results in a flat line for the Nalgene™ reusable bottle no matter how many times it is refilled.
Figure 5: Cumulative GHG Impact: Consumption of 500ml of Water
The initial investment in a reusable bottle pays off quickly: we need only use it three times over the purchase of imported water to accumulate less embodied carbon. We would need to reuse a Nalgene™ bottle just more than six or nine times to have a lower footprint than domestically sourced water bottled in virgin or recycled PET. Given that such containers sell for $10 or more, it is likely that we would break even environmentally before we do financially.
While metal or glass containers will have different footprints, the environmental benefit of using reusable drinking containers will be even more advantageous than it is for shopping bags, with one study showing it may take more than 170 uses to offset the investment in a cotton bag over the typical HDPE bags provided at checkout. This is understandable since the transportation of water is inherently emissions intensive. For example, even though the domestic water is sourced from relatively nearby springs, the transport of the water comprises over 20% of the total footprint, while the pumping and treatment of the water is less than 1%. Other domestic brands that use out of state water sources will have a higher transportation footprint.
Conclusions
In summary, the best choice for hydration is to develop a habit of bringing along a reusable container. If that is not an option, then buy a brand of bottled water that is more locally sourced, as distance has a larger impact than the percent of recycled content in the bottle. Imported water should be consumed sparingly, regardless of how it is packaged. Thankfully, imported bottled water has a small and shrinking share of the overall market for still water: only one brand (Fiji) is represented in the top brands that comprise 75% of the US market, and it has a small (3%) share.
Table 1: What-if analysis for alternate purchasing behavior
Americans currently purchase an average of 36.5 gallons of bottled water annually, about 275 500ml bottles. While some purchases of single-use water bottles may be necessary, if 200 million Americans obtained a reusable container and replaced half of their yearly bottled water purchases by refilling these containers at taps or drinking fountains, Table 1 shows we could avoid over 1.3 million metric tons of CO2e emissions annually. While this represents only 0.025% of the national annual emissions, this would be a relatively painless behavior to adopt. Small drops do add up.
