Global Warming Potential

Global warming potential (GWP) is defined as the cumulative radiative forcing, both direct and indirect effects, over a specified time horizon resulting from the emission of a unit mass of gas related to some reference gas [CO2: (IPCC 1996)].

From: Environmental Management, 2017

Air pollution biogeochemistry

Daniel A. Vallero, in Air Pollution Calculations, 2019

8.3.2 Global warming potential

Greenhouse gases warm the earth by absorbing energy and decreasing the rate at which the energy escapes the atmosphere. These gases differ in their ability to absorb energy, that is, they have various radiative efficiencies. They also differ in their atmospheric residence times. Each gas has a specific global warming potential (GWP), which allows comparisons of the amount of energy the emissions of 1 ton of a gas will absorb over a given time period, usually a 100-year averaging time, compared with the emissions of 1 ton of CO₂.

Because CO₂ has a very long residence time in the atmosphere, its emissions cause increases in atmospheric concentrations of CO₂ that will last thousands of years [8]. Methane’s average atmospheric residence time is about a decade. However, its capacity to absorb substantially more energy than CO₂ gives it a GWP ranging from 28 to 36. The GWP also accounts for some indirect effects; for example, CH₄ is a precursor to another greenhouse gas, ozone.

The GWP of N₂O is 265–298 times that of CO2, with an average residence time of 100 years. The CFCs, hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF₆) are referred to as high-GWP gases, that is, GWP can be up to tens of thousands. For a given amount of mass, they hold substantially more heat than does CO₂.

What happens to the methane GWP if a 20-year averaging time is used?

A 20-year GWP is sometimes used as an alternative to the 100-year GWP. The 20-year GWP is based on the energy absorbed over 20 years, which prioritizes gases with shorter lifetimes, since it ignores any impacts that occur after 20 years from the emission. The GWPs are calculated relative to CO₂, so the GWPs are based on an 80% shorter time frame that will be larger for gases with atmospheric residence times shorter than that of CO₂ and smaller for gases with residence times greater than CO₂.

Since CH₄ has a shorter atmospheric residence time than CO₂, the 100-year GWP is much less than the 20-year GWP. The CH₄ 20-year GWP has been estimated [8] to be 84–87, compared with the 100-year GWP of 28–36.

What happens to the GWP for the simplest fluorocarbon, tetrafluoromethane (CF₄), if a 20-year averaging time is used?

The estimated atmospheric residence time for CF₄ is 50,000 years [8]. The 100-year GWP is estimated to range from 6630 to 7350, which is larger than the 20-year GWP of 4880–4950. Therefore, the shorter averaging time gives a 100-year GWP that is much larger than the 20-year GWP.

An alternate metric is the global temperature potential (GTP). Unlike the GWP, which is a measure of the heat absorbed over a given time period due to emissions of a gas, the GTP is a measure of the temperature change at the end of that time period relative to CO₂. The calculation of the GTP is more complicated than that for the GWP, based on models of response of the climate system to increased greenhouse gas concentrations, that is, climate sensitivity, and the amount of time it takes the system to respond, especially on the oceans’ capacity to absorb the heat [8].

Carbon dioxide equivalency (CDE) is one way to estimate how much CO₂ would be needed for a mixture of emissions to have the same GWP, if measured over a defined period of time, most often 100 years. CDE, then, is the time-integrated radiative forcing of a quantity or rate of gas emissions to the troposphere. It is not an instantaneous value of the radiative forcing by a concentration of greenhouse gases in the atmosphere. The CDE is the product of the greenhouse gas mass (in million metric tonnes) and GWP. A company is proposing to produce 500 kg per year of a refrigerant gas mixture containing 10% sulfur hexafluoride (SF₆), 40% perfluorohexane (C₆F₁₄), and 50% difluromethane (CH₂F₂; also known as hydrofluorocarbon-32). What is the CDE for this mixture?

Using data from the Intergovernmental Panel on Climate Change (IPCC) [9], the 100-year GWP values for these gases are

SF₆: 22,800

C₆F₁₄: 9300

CH₂F₂: 679

Calculate the gas mixture GWP for the mixture ratio:

(0.1 \times 22800) + (0.4 \times 9300) + (0.5 \times 675) = 2280 + 3720 + 337.5 = 6337.5

Multiply the mixture GWP times the mass to obtain the CDE. For industrial emissions, CO₂ equivalents are often expressed as “million metric tonnes of carbon dioxide equivalents” (MMTCDE):

500 kg = 5 \times 10^{- 7} million tonnes

MMTCDE = 6337.5 \times (5 \times 10^{- 7}) = 3.17 \times 10^{- 3}

Since this is equilibrated to CO2, that is, the 100-year GWP = 1, this means that the annual addition of this newly formulated gas mixture to the atmosphere is equivalent to 0.0317 million metric tonnes of CO₂.

View chapter Explore book

Read full chapter

URL: https://www.sciencedirect.com/science/article/pii/B9780128149348000089

US and global environmental regulations

John Durkee Ph.D., P.E., in Management of Industrial Cleaning Technology and Processes, 2006

2.3.6 Regulation of Solvent Cleaning⁹⁰ Because of Global Warming

Global Warming Potential (GWP)⁹¹ has been developed as a metric to compare (relative to another gas) the ability of each greenhouse gas to trap heat in the atmosphere. Carbon dioxide (CO₂) was chosen as the reference gas to be consistent with the guidelines of the Intergovernmental Panel on Climate Change (IPCC⁹²).

GWPs of common solvents which are important⁹³ to persons doing solvent cleaning are given in Table 2.11,⁹⁴,⁹⁵,⁹⁶ with that of other compounds of interest.

Table 2.11. GWP at 100 Year Time Horizon

Compound Name	Formula	Source	Application	SAR	TAR
Carbon dioxide	CO₂	Natural	Human respiration	1	1
Methane	CH₄		Bacterial activity	21	23
Nitrous oxide	N₂O		Fertilizers wastes	310	296
HFE-8200		Manmade	Cleaning agent		55
HFE-7200	C₄H₉OCH₃		Cleaning agent
HCFC-225ca/HCFC-225cb	CF₃CF₂CHCl₂ CClF₂CF₂CHClF		Cleaning and drying agent	181/620
HFC-23	CHF₃			11 700	12000
HFC-32	CH₂F₂			650	550
HFC-125	CF₃CHF₂			2800	3400
HFC-134 a	CF₃CH₂F		Refrigerant	1300	1300
HFC-143 a	CF₃CH₃			3800	4300
HFC-152 a	CH₃CHF₂			140	120
HFC-227 ea	CF₃CHFCF₃		Fire extinguishant refrigerant	2900	3500
HFC-236 cb	CF₃CF₂CH₂F				1300
HFC-236 ea	CF₃CHFCHF₂				1200
HFC-236f a	CF₃CH₂CF₃		Fire extinguishant refrigerant	6300	9400
HFC-245 ca	CH₂FCF₂CHF₂			560	640
HFC-245 fa	CHF₂CH₂CF₃		Blowing agent		950
HFC-365 mfc	CF₃CH₂CF₂CH₃		Cleaning and drying agent		890
HFC-43-10mee	CF₃CHFCHFCF₂CF₃		Cleaning and drying agent	1300	1500
Sulphur hexafluoride	CF₆		Enchant in manufacture of semiconductors	23 900	222 00
CFC-113	CCl₂FCClF₂		Cleaning agent whose manufacture is banned because of ODP
Carbon tetrafluoride	CF₄			6500	5700
Perfluoroethane	C₂F₆			9200	119 00
Perfluoropropane	C₃F₈		Drying agent heat transfer fluid	7000	8600
Perfluorobutane	C₄F₁₀			7000	8600
Perfluoro-cyclobutane	c-C₄F₈			8700	10 000
Perfluoropentane	C₅Fl₂			7500	8900
Perfluorohexane	C₆Fl₄			7400	9000

One of the points that should be taken from Table 2.11 is that global warming is an evolving science. That's why GWP values from the Third Assessment Report (TAR) are different from values published in the Second Assessment Report (SAR).

A second point, supporting Figure 2.20,⁹⁷ is that global warming would not be a problem where there is no human life about Planet Earth!

Said another way, both involuntary (non-discretionary) and voluntary (discretionary) human activities contribute to global warming.

There is only a portion of this serious problem on which humans can modify their activities to contribute to a solution.

2.3.6.1 High Concern – High GWP Gases

The gases of concern in Table 2.11 are the HFCs and PFCs. They are called high-GWP gases.

By application, most of these solvents are refrigerants.

Even on the basis of Carbon equivalents,⁹⁸ not actual volume emitted, these gases with high-GWP ratings are not a major contributor to the inventory of greenhouse gases. The blue exploded sector (2.02%) in Figure 2.20 shows actual emission (in Carbon equivalent units) in 1999 by source or type⁹⁹ of emission.

Given the distribution of applications for HFCs/PFCs/SF₆, solvent use is still a minor segment. Figure 2.21 (see Footnote 36) shows the distribution of estimated emissions of fluorinated fluids in 2010. The percentages are based on Carbon-equivalents, not volumes of gases.

Within that distribution, refrigerant use dominates 45%). Solvent use, not just for cleaning applications, is only around 3% of the Carbon-equivalent emission.

2.3.6.2 “Why are THEY Picking on Us?”

No single cleaning solvent is a major contributor to the problem of global warming – based on GWP rating and emission volume.

Use of HFCs, PFCs, and SF₆ draws concern, from environmental regulatory agencies, out of proportion to their volume (or Carbon-equivalent volume) of emission.

There are several reasons for a high level of concern by environmental regulatory agencies:

•: Use is controllable with moderate regulatory effort. Contrast regulation of CO₂ emissions from human respiration or photosynthesis in plant life; regulation of CH₄ emissions from animals; regulation of N₂O emissions from combustion of forests, with regulation of use of a chemical whose production can be restricted (or banned) by fiat, or whose use can be managed through choices of process equipment. With this perspective, focus on high-GWP gases is a sound regulatory strategy.
•: Use of fluorinated gases is growing at an aggressive rate. That rate is expected to accelerate faster than general economic growth (see Figure 2.22 and Footnote 36). The HFC category is expected to grow from less than 10 MMTCE to more than 50 in 20 years. A major reason for growth of use of HFCs and PFCs is that they replace other substances which are CFCs (CFC-113 and HCFC 141b).
Figure 2.22. Growth of use of fluorinated gases
•: Regulation is consistent with the economic preferences of users. HFCs and PFC are quite expensive (€15–€20 per pound as of Fall 2003). Users have a real incentive not to emit them. Most applications, except for actions such as suppression of fires, are in equipment which contains emissions.
•: Fluorinated gases have higher GWP values than other substances – see Table 2.11. Their use commands attention.

In summary, the focus on HFCs, PFCs, and SF₆ will continue to be out of proportion to their inventory in the atmosphere.

View chapter Explore book

Read full chapter

URL: https://www.sciencedirect.com/science/article/pii/B9780080448886500168

Chlorofluorocarbons

W.T. Tsai, in Encyclopedia of Toxicology (Third Edition), 2014

Environmental Hazards

GWP expresses the relative increase in earthward IR radiation flux due to the emission of organic compounds. Notably, all CFCs have high GWP values relative to the reference compound, carbon dioxide (seen in Table 1). Furthermore, these saturated halocarbons are considered not easily biodegradable based on the data of octanol/water partition coefficients also listed in Table 1. With respect to ecotoxicity, it was also revealed to be not very toxic to aquatic organisms (i.e., algae, water fleas, and fish) and terrestrial plants. For example, CFC-113, which was one of the most used solvents, shows a very low toxicity toward aquatic species such as Daphnia and fish. As described, the most significant environmental hazard for CFCs should be the ozone depletion, which is caused by chlorine molecules in these so-called ozone-depleting substances that migrate to the stratosphere and then react catalytically with ozone, thus destroying it. In addition, from the view of the effect on air quality, CFCs have been listed as having ‘negligible photochemical reactivity’ and do not contribute to smog formation and ground-level ozone. Therefore, they are exempt from volatile organic compound regulations according to the US Clean Air Act Amendments of 1990.

View chapter Explore book

Read full chapter

URL: https://www.sciencedirect.com/science/article/pii/B9780123864543011180

Environmental impact assessments of compressed air energy storage systems: a review

Md Mustafizur Rahman, ... Amit Kumar, in Environmental Assessment of Renewable Energy Conversion Technologies, 2022

11.5.1 Greenhouse gas emissions

GWP is the most widely used impact category in the reviewed studies evaluating CO₂ equivalents considering CO₂, CH₄, and N₂O emissions. Fig. 11.4 shows the GHG emissions of different ESS systems. A few studies presented only point estimates, and others provided a range of emissions. The life cycle GHG emissions are hugely influenced by the use phase (where electricity is used for charging). For instance, in A-CAES, about 98% of the total life cycle GHGs are emitted in the use phase, while the rest, 3%, are from construction and decommissioning (Kapila et al., 2019). It is important to mention that use-phase GHG emissions depend on the electricity source. The cleaner the electricity production, the lower the life cycle GHG emissions. In Fig. 11.4, the bars for the study by Oliveira et al. (2015) represent life cycle GHG emissions ranges for different ESSs considering several sources of electricity (i.e., solar, wind, and grid mix). For example, the total GHGs for PHS ranges from 23.5 to 650 kg-CO₂equiv./MWh. While the infrastructure emissions are only about 5 kg-CO₂equiv./MWh, the GHG emissions for electricity use range from 18.5 kg CO₂equiv./MWh for the wind to 645 kg-CO₂equiv./MWh for UCTE mix. The technical parameters, such as efficiency, depth of discharge, and lifetime, also influence the total life cycle GHG emissions. For example, the life cycle GHG emissions of PHS (211 kg-CO₂equiv./MWh) are less than those of the A-CAES (232 kg-CO₂equiv./MWh) system; this is because PHS has a longer lifetime (60 years) than C-CAES (40 years) (Kapila et al., 2019).

It is clear from the above discussion that comparing only the infrastructure emissions can help understand the environmental performance of different storage technologies. Using the same system boundary for the technologies they compared, Denholm and Kulcinski (2004) estimated the GHG emissions of C-CAES, PHS, and VRFB. Electricity production emissions excluded, Denholm and Kulcinski (2004) found the highest GHG emissions in C-CAES and the lowest in PHS. While the GHG emissions for PHS and VRFB are from material and energy use in construction, the emissions in C-CAES include both construction and natural gas emissions. Of the mechanical storage systems, PHS performs better because it has a longer lifetime than other systems and does not use fossil fuels. As reported by Oliveira et al. (2015), the infrastructure emissions of electrochemical batteries are higher than those of mechanical ESSs because the batteries have a lower lifetime and use energy-intensive chemicals. The GHG emissions of C-CAES and PHS are 8 and 5 kg-CO₂equiv./MWh, respectively, while the GHG emissions of PbA, Li-ion, and Na-S are 102, 63, and 23 kg-CO₂equiv./MWh, respectively, for infrastructure only (Oliveira et al., 2015). The emissions reported by Denholm and Kulcinski (2004) and Sternberg and Bardow (2015) for VRFB are in good agreement. Although the total life cycle GHG emissions of PbA, Na–S, and Li-ion reported by Hiremath et al. (2015) are higher than those reported by Oliveira et al. (2015) due to the differences in electricity mix emissions, the GHG emissions for storage infrastructure are in good agreement.

View chapter Explore book

Read full chapter

URL: https://www.sciencedirect.com/science/article/pii/B9780128171110000036

Global gases

Wendy H. Yang, ... Gavin McNicol, in Principles and Applications of Soil Microbiology (Third Edition), 2021

The concept of global warming potential is used to balance the ecosystem exchanges of multiple greenhouse gases, including carbon dioxide, methane, and nitrous oxide. Methane traps more heat than carbon dioxide on a per molecule basis, meaning that it has a higher global warming potential. However, this difference in global warming potential effectively becomes smaller over time because methane has a relatively short atmospheric lifetime (9 years). The time horizon considered is crucial in understanding how wetland drainage changes affect total global warming potential. Over years to decades, the high global warming potential of methane emitted from re-flooded wetlands can offset the negative carbon dioxide emissions associated with slowed organic matter decomposition. Thus, in the short term, the global warming potential of re-flooded wetlands is often greater than that of drained wetlands, where methane emissions are low. However, over centuries to millennia, the global warming potential of methane becomes much smaller and is typically more than offset by the long-term uptake of atmospheric carbon dioxide in plant biomass and its storage in soil organic matter. A further consideration is that agricultural fertilizer application to drained wetlands will increase soil emissions of nitrous oxide, which is even more effective than methane at trapping heat. In contrast, nitrous oxide emissions from consistently flooded wetlands are typically small. Therefore, we should consider the long-term effects of land use changes on all potentially important trace gases.

View chapter Explore book

Read full chapter

URL: https://www.sciencedirect.com/science/article/pii/B9780128202029000204

Water-Quality Engineering

T.A. Larsen, M. Maurer, in Treatise on Water Science, 2011

4.07.5.3.3 On-site uncontrolled anaerobic digestion

Considering the high global warming potential (GWP) of methane, it is surprising that widespread on-site technologies for disposal of domestic wastewater still rely on uncontrolled anaerobic digestion. For septic tanks, the methane production depends on the subsurface temperature (see Section 4.07.5.3.1), whereas the better-controlled johkasous are more likely to give rise to methane gas production. We therefore briefly illustrate the implications of uncontrolled methane production from on-site reactors. Since it is difficult to obtain any exact data on sedimentation in septic tanks and johkasous, let alone data on anaerobic degradability, we only present specific data and one example based on primary sedimentation in treatment plants (Table 10). Methane production from COD elimination is based on the concept of mass conservation of theoretical COD (Gujer and Larsen, 1995). The GWP is presented for a time period of 20 and 100 years (the latter timescale normally being considered of relevance). For comparison, we also present the GWP of electricity production, because electricity is the dominant energy form used for wastewater treatment technologies. Obviously, the net greenhouse gas emission from electricity production greatly varies (from close to zero for renewable energy sources to about 1 g CO₂/Wh for small coal-fired power plants; Bettle et al., 2006); however, for simplicity, we use a value corresponding approximately to the European electricity mix (0.8 g CO₂/Wh; European Environmental Agency, 2002).

Table 10. The global warming potential (GWP) of uncontrolled anaerobic degradation of COD from combined domestic wastewater

GWP(20) of CH₄ (timescale 20 years)	$g_{{CO}_{2}} / g_{{CH}_{4}}$	72	a
GWP(100) of CH₄ (timescale 100 years)	$g_{{CO}_{2}} / g_{{CH}_{4}}$	25	a
Specific CH₄ production from COD	$g_{{CH}_{4}} / g_{COD}$	0.25	b
Specific GWP(20) of methane production from COD	$g_{{CO}_{2}} / g_{COD}$	18
Specific GWP(100) of methane production from COD	$g_{{CO}_{2}} / g_{COD}$	6
Specific production of COD	g_COD/cap/day	120	a
Assumed primary sludge production (25% of COD)	g_COD/cap/day	30	a
Assumed primary sludge degradation (50% of sludge)	g_COD/cap/day	15	d
GWP(20) based on assumptions above	$g_{{CO}_{2}} / cap$	270
GWP(100) based on assumptions above	$g_{{CO}_{2}} / cap$	90
Specific CO₂ production from electricity production	$g_{{CO}_{2}} / Wh$	0.8	e
CO₂ production from typical 10 W/cap WWTP	$g_{{CO}_{2}} / cap$	192	f

a: IPPC (2007: ch. 2, p. 212).
b: Based on a mass conservation of theoretical COD (Gujer and Larsen, 1995).
c: From Table 8.
d: Typical values from centralized treatment of municipal wastewater (Gujer, 2007). Note that the anaerobic degradability is for primary and secondary sludge; for primary sludge it will be higher.
e: Based on EU 15 electricity mix from 1997 (European Environmental Agency, 2002).
f: A typical advanced wastewater treatment plant (WWTP) consumes around 10 W/person of electrical power (1 W/cap=24 Wh/cap/day).

From Table 10, we can get an idea whether methane production from on-site anaerobic degradation of primary sludge is relevant or not. A typical modern wastewater treatment plant has an electricity consumption of about 10 W/person (corresponding to 240 Wh/cap/day), whereas the membrane johkasous are about 3 times as energy intensive (Table 9). We thus see that in the short term (20-year timescale), the GWP of methane production from primary sludge is similar to the GWP arising from electricity use in a modern centralized treatment plant. Due to the much shorter lifetime of methane in the atmosphere, it is obvious that the longer the time horizon, the smaller the contribution will appear. In conclusion, from a global warming perspective, the energy use for enhanced treatment is justified, especially if the electricity used has a small carbon dioxide footprint.

One way of reducing anaerobic digestion of primary sludge in johkasous, for example, is denitrification in the sludge compartment as described in Section 4.07.5.3.2. In septic tanks, at least, where nitrification and recycling of nitrified wastewater are difficult, separate nitrification of urine could be a good alternative. From Table 9 it can be concluded that about 10 g of ${NO}_{3}^{-}$ N/cap/day can be removed by denitrification, corresponding to around 29 g/cap/day of COD removal (based on mass conservation of theoretical COD; Gujer and Larsen, 1995). In principle, this would be more than enough to suppress anaerobic degradation of primary sludge, even if the assumptions made in Table 10 are conservative. More detailed investigations would however be necessary to test these assumptions, and obviously denitrification processes may also give rise to global warming, if not properly controlled.

View chapter Explore book

Read full chapter

URL: https://www.sciencedirect.com/science/article/pii/B978044453199500083X

Physical drivers of climate change

Kieran Ohara, in Climate Change in the Anthropocene, 2022

2.4 Global warming potential

The concept of global warming potential (GWP) was introduced in IPCC-AR1 (Shine et al., 1990) to compare the greenhouse effects of different greenhouse gases relative to a reference gas, normally taken as carbon dioxide. Under this definition, CO₂ would have a GWP value of 1. It is defined as:

(2.2)

G W P = \frac{\int_{0}^{a} a_{i} c_{i} d t}{\int_{0}^{a} a_{c o_{2}} c_{c o_{2}} d t}

where a_i is the instantaneous radiative forcing (RF) due to increase in concentration of gas i, c_i is the concentration of the gas remaining after time t and n is the number of years over which the calculation is performed. The corresponding values for the reference gas (CO₂) are in the denominator. It is assumed the gas is released instantaneously into the atmosphere and that its concentration decreases over time and during this time it produces greenhouse warming. If it is assumed gas i is removed only in proportion to its concentration then:

(2.3)

c_{i} (t) = e^{- t / τ}

where τ is the average lifetime of the gas in the atmosphere (Lashof and Ahuja, 1990). The GPW concept is useful in estimating the cumulative radiative forcing of all the greenhouse gases together at the same time (see Chapter 7).

The assumption of exponential decrease appears to be fulfilled by N₂O and CFCs (chloroflurocarbons). The case of CO₂ is more complex as it does not have a well defined residence time since it is transferred between different reservoirs on different timescales (ocean, land, biota, atmosphere). Because of this, using carbon dioxide as the reference gas above may not be an optimal choice. Additional problems are the indirect effects on RF due to CH₄ -CO-OH reaction coupling. Methane emissions tend to increase tropospheric ozone and stratospheric water vapor possibly enhancing the indirect greenhouse effect of methane.

In physical terms, the GWP can be interpreted as an index of the total energy added to the climate system by a greenhouse gas relative to that of CO₂ (Myhre et al., 2013). These authors give the GWP value of methane as 84–86 over 20 years and 28–34 over 100 years. Nitrous oxide values over the same time periods are 264–268 and 265–298, respectively. The ranges in estimates are largely due to models that account for, or do not account for, climate-feedback mechanisms. These values are not that different from the early values given in the first IPCC report (Shine et al., 1990), but they are still relatively tentative. Some of the properties of the main greenhouse gases are described below.

View chapter Explore book

Read full chapter

URL: https://www.sciencedirect.com/science/article/pii/B9780128203088000118

Transition of Plastics to Renewable Feedstock and Raw Materials: Bioplastics and Additives Derived From Natural Resources

Michel Biron, in A Practical Guide to Plastics Sustainability, 2020

10.10.5 Examples of Environmental Advantages

Main indicators, global warming potential (GWP) and energy consumption, are benefiting for bio-PUR made out of natural sourced polyol. For example:

•: GWP (kg CO₂ eq/kg PUR) is claimed 2.18 for Lupranol Balance 50 versus 2.99 for a traditional PUR
•: Lupranol Balance 50 consumes 12% less energy than similar traditional PUR.

Some other indicators are also better for natural sourced PUR, for example:

•: Ozone depletion potential (CFC eq g/t polyol) 4 versus 7 for traditional PUR
•: Acidification (SO₂ eq kg/t polyol) 17.6 versus 19
•: Critical water volume (norm. m³/t polyol) 929 versus 1239
•: Solid waste (norm. t/t polyol) 0.11 versus 0.22

For other examples:

•: For a 47% renewable content based on MB concept, calculated GHG values are 2.1 kg CO₂ eq/kg (Cradle to Grave: Evyron) versus 3.5 for undefined traditional PUR
•: For 16%–17% renewable contents based on MB concept, calculated GHG values are 2.5 kg CO₂ eq/kg (Cradle to Grave: Evyron)

For polyols or PUR containing some CO₂, benefits depend on the used replacement level and the considered end products. For example:

•: GHG emissions may be 2.6–3.03 kg CO₂ eq/kg of polyols versus 3.2–3.4 for traditional polyols
•: Fossil resource depletion in kg oil eq may be 1.5–1.87 versus 1.94 for equivalent conventional PUR.

View chapter Explore book

Read full chapter

URL: https://www.sciencedirect.com/science/article/pii/B9780128215395000100

Environmental and Related Biotechnologies

V. Diamantis, ... S.E. Vlaeminck, in Comprehensive Biotechnology (Third Edition), 2011

6.35.2.5 Nitrous Oxide Emissions From Waste Biodegradation

Since 1 kg N₂O has a GWP of 310 kg CO₂ on a time horizon of 100 years,¹⁷ N₂O emissions during biological nitrogen removal can weigh heavily on the overall CO₂ footprint of a wastewater treatment plant. The production of N₂O can be related to nitritation, that is, ammonia oxidation to nitrite, or to denitrification. For both processes, N₂O emissions are stimulated by rapidly changing process conditions and by high nitrite levels. Furthermore, high DO levels and low COD/N ratios enhance denitrification emissions, whereas high ammonium concentrations (also simultaneously with nitrite) and specific (about 1 mg O₂ l⁻¹) or changing (low to high) DO levels increase nitritation emissions.¹⁸ Given the highly dynamic nature of N₂O emissions, accurate quantifications can only be obtained from grab samples taken at high frequency or from continuous online measurements.¹⁸ Only some reports exist using this approach on full-scale wastewater treatment plants (WWTPs), displaying a wide range of N₂O emissions: from 0.01% to 3.3% of the nitrogen load.^19,20 Assuming a nitrogen load equal to 0.013 kg total ammonia nitrogen (TAN) IE⁻¹ day⁻¹, the amount of N₂O generated annually is 0.475–157 g N₂O IE⁻¹ year⁻¹ or 0.23–76 kg CO₂ IE⁻¹ year⁻¹.

View chapter Explore book

Read full chapter

URL: https://www.sciencedirect.com/science/article/pii/B9780444640468003736

How can we validate the environmental profile of bioplastics? Towards the introduction of polyhydroxyalkanoates (PHA) in the value chains

Alba Roibás-RozasMateo Saavedra del OsoGiulia ZarroliMiguel Mauricio-IglesiasAnuska Mosquera-CorralSilvia FioreAlmudena Hospido, in Assessing Progress Towards Sustainability, 2022

Impact categories

The most assessed impact category is Global Warming Potential (GWP), as it is expected that bioproducts can mitigate the effect of climate change. Non-renewable Energy Use (NREU) or Fossil Resource Depletion is also commonly evaluated as bioplastics would replace petrochemical materials. Acidification and Eutrophication Potential were also commonly studied, and just a few papers reviewed an important number of the categories included in the ReCiPe impact methodology (Fernández-Braña et al., 2019; Harding et al., 2007; Roibás-Rozas et al., 2020; Vega et al., 2020; Vogli et al., 2020).

Again, the lack of data regarding EoL affects the selection of impact categories, as it is not completely clear how the effects linked to polymer production, use, and disposal are transferred on the environmental compartments. On the other hand, the JRC-EC method states that the whole 16 categories addressed in the Product Environmental Footprint Guidelines (Manfredi et al., 2012) need to be considered, so each of them must be discussed in LCA studies from now on. In any case, it has been stated that, when the LCA is performed for polymers processed from crops, categories such as Land Use, Acidification, and Eutrophication must be mandatorily considered (Heimersson et al., 2014).

View chapter Explore book

Read full chapter

URL: https://www.sciencedirect.com/science/article/pii/B9780323858519000109