Life Cycle Beef Greenhouse Gas Emission

Introduction

Cultured meat is an emerging technology in which animal musculus cells are produced through tissue civilisation in a controlled manufactory or laboratory environment, in dissimilarity to traditional whole-animal livestock systems (Stephens et al., 2018). Other commonly used terms include clean, in vitro, lab-grown, or synthetic meat. Reducing the environmental impacts of meat production, and particularly greenhouse gas (GHG) emissions, is generally highlighted as a significant potential advantage of cultured meat (Tuomisto and Teixeira de Mattos, 2011; Post, 2012). Despite recent research and pop interest in cultured meat, and the frequency with which its supposed climate benefits are reported, the potential temperature impacts of cultured meat production have not yet been investigated.

Livestock production systems are associated with a number of GHG emissions, and take made a significant contribution to anthropogenic climate change (Reisinger and Clark, 2018). Broadly, the livestock themselves result in emissions of methane (CH₄) and nitrous oxide (Northward₂O) from their manures, and further methyl hydride from enteric fermentation in ruminants. Farther GHGs associated with, simply not directly emitted by, animate being production include the loss of nitrous oxide from fertilizer application to grow their feed, carbon dioxide (CO_ii) emissions from the conversion of country for pasture or feed production, and CO_ii emissions resulting from fossil fuel based energy generation, for example in tractor fuels or the manufacture of fertilizers (in addition to by-product CO_two also formed in fertilizer production, Dawson and Hilton, 2011). While there is a very large range in emissions associated with different beast production systems, they are generally shown to emit significantly more per unit of measurement of food output (for example emissions per kg final product or per kg poly peptide) than establish-based systems, and beef is typically highlighted as among the most emission intensive food products (Clune et al., 2017; Poore and Nemecek, 2018).

Proponents of cultured meat accept suggested that bypassing the wider biological processes of the whole animate being can upshot in lower emissions per unit of meat produced, as the direct animal emissions are avoided, and cultured systems could be designed to more efficiently convert inputs into the desired output (meat), thus minimizing the emissions associated with the production of these inputs. A trade-off may exist in significant free energy demand to maintain the controlled manufacturing surround that essentially replaces some of the animal'due south biological functions (Mattick et al., 2015b); and large uncertainties remain in what viable, animal-free, growth media may look like (Stephens et al., 2018) and hence their potential resource need.

Despite the remaining unknowns in large-scale cultured meat production, a small-scale number of studies have undertaken speculative life cycle assessments (LCA) to predict the ecology footprint of cultured meat (Tuomisto and Teixeira de Mattos, 2011; Tuomisto et al., 2014; Mattick et al., 2015b; Smetana et al., 2015). The suggested GHG emissions per unit of cultured meat produced ("carbon footprints") vary significantly, every bit they are based on dissimilar production systems and assumed inputs, and take alternative approaches in anticipating future developments. Even so, the GHG emissions per unit of cultured meat are uniformly shown as superior to that of beefiness where this comparison is fabricated (trends are less articulate for other animal products).

To date, these comparisons (and most others evaluating the relative emissions intensity of different products or activities) are based on carbon dioxide equivalent (CO_iidue east) metrics that chronicle the emissions of unlike GHGs to carbon dioxide. However, such metrics may be misleading, and provide a poor indication of actual temperature response (Pierrehumbert, 2014). Private gases differ both in the corporeality they change the atmospheric free energy balance (radiative forcing), and hence lead to warming, and how long they persist in the atmosphere. Per molecule, marsh gas results in significantly greater radiative forcing than carbon dioxide, but has an atmospheric lifespan of just effectually 12 years (Myhre et al., 2013) in contrast to the millennial persistence of carbon dioxide (Archer and Brovkin, 2008). Nitrous oxide has a much greater radiative forcing per molecule than both marsh gas and carbon dioxide, and an atmospheric lifetime of just over 100 years (Myhre et al., 2013). The most commonly used carbon dioxide equivalence metric, the 100-years Global Warming Potential (GWP₁₀₀), equates each gas by integrating the amount of radiative forcing that a ane-off emissions pulse would exert over a 100-years period (Myhre et al., 2013). If we are to consider the climate effects of ongoing production, however, we need to consider the impact of connected emissions rates of each gas. GWP₁₀₀ based comparisons, among other limitations, do not sufficiently capture the temporal behavior of different gases, and in particular neglect to express the cumulative nature of continued carbon dioxide emissions, and hence tin can relatively overstate the warming touch of methane (Pierrehumbert, 2014). Additionally, due to the short lifetime of methane, whatever warming information technology causes is largely undone shortly after emissions are removed, in contrast to carbon dioxide. Inferring relative temperature impacts from GWP₁₀₀ footprints can therefore be particularly problematic where short-lived gases such as methane constitute a significant proportion of emissions, as is the instance for beef product.

This paper presents the starting time attempt to compare the potential climate impacts of cultured meat and beefiness cattle production using an atmospheric modeling approach, rather than relying on carbon dioxide equivalent comparisons. Nosotros test a number of cultured meat and beef system emissions footprints under three alternative consumption pathways, comparing the temperature impacts nether different production and consumption scenarios at all timescales to 1,000 years.

Methods

In order to ensure standardization, the atmospheric models, consumption pathways, and representative cattle production emissions all follow Pierrehumbert and Eshel (2015).

A literature review was undertaken in April 2018 to screen for cultured meat emissions footprints. Every bit considerable uncertainty remains over what real, big-scale cultured meat production may look like, four different footprints plant in this literature review were used to illustrate some of the possibilities.

The first cultured meat LCA study, presented in Tuomisto and Teixeira de Mattos (2011), hypothesized a system in which animal embryonic stem cells are grown in a cylindrical stirred tank bioreactor in a medium of cyanobacteria hydrolysate (as the main "feed" input), vitamins and animal growth factors. Animal growth factors are produced from genetically engineered Escherichia coli, and both growth factors and vitamins are considered to be required in negligible volumes, and hence incur negligible environmental impacts (including GHG emissions). The cyanobacteria production is causeless to have place in an open up pond, with some synthetic nitrogen use considered in the default example, but either nitrogen-fixing blue-green alga or "nutrient-rich wastewater" used to eliminate the need for fertilizer inputs in the nigh optimistic scenarios. Greenhouse gas emissions result primarily from energy use and send in growing and moving the cyanobacteria to the site of cultured meat production, followed by energy use in cyanobacteria processing and stirring the prison cell civilisation tank for 60 days. Balance estrus following cyanobacteria hydrolysate sterilization initially warms the civilisation medium, and following this it is assumed oestrus generated by the metabolism of cells growing in the civilization negates the need for external heating. Greenhouse gas footprints were and then estimated based on the conditions and emissions per unit of measurement of energy utilisation for 3 representative regions (Thailand, California, and Spain), with emissions from electricity generation lowest in Thailand and highest in California. The cultured meat output assumed as the functional unit of measurement was a "minced-beef type" production with equivalent protein content to low fatty meat. For farther details come across Tuomisto and Teixeira de Mattos (2011). Post-obit through the assumed yields and allocation conventions used in this study (come across give-and-take below), the average emissions footprint was approximately 2.01 kg CO_twoe per kg cultured meat. As this report represents the most optimistic scenario, we apply the lowest value presented in the sensitivity analysis of i.69 kg CO_twoeastward per kg cultured meat, assuming no fertilizer use was necessary for cyanobacteria production and electricity generation uses the everyman Thai emissions footprint. It was non possible to divide out individual greenhouse gases, and then it is causeless that the unabridged footprint is carbon dioxide emissions. As at that place was no fertilizer use in the footprint used, and in alternative footprints below other emissions represent relatively small proportions of the total footprint, this assumption is unlikely to significantly affect the results.

The second cultured meat footprint used in this written report was obtained from Tuomisto et al. (2014). The hypothesized systems are largely as described higher up from Tuomisto and Teixeira de Mattos (2011), but with some refinements fabricated to the assumed operation of the bioreactor, and a number of plant-based alternative feedstocks considered in addition to cyanobacteria. Wheat or maize feedstocks were assumed to have been grown with the GHG footprints of typical Great britain production from Williams et al. (2006) and sterilized and hydrolyzed as described above for blue-green alga. A hollow capillary bioreactor was selected to correspond a superior option to the stirred cylinder design above, but in this example as well included an energy input in maintaining growth temperature (37°C) for cultured cells. As this written report still represents an optimistic just potentially more than realistic footprint than suggested past Tuomisto and Teixeira de Mattos (2011), an intermediate value of 3.67 kg CO_twoe per kg cultured meat was selected from the range of results presented, assuming maize feedstock (with a greater product footprint than blue-green alga only less than wheat), and an average of the best- and worst-instance bioreactor yield scenarios. This footprint is also assumed to be equanimous entirely of carbon dioxide emissions. In practice, nitrous oxide emissions would too be expected from a proportion of the nitrogen inputs in growing maize, but it was non possible to divide out this component of emissions. The omission is over again considered unlikely to significantly influence conclusions, as discussed beneath in the context of results for other cultured meat systems.

The remaining two cultured meat footprints were both taken from Mattick et al. (2015b). In this study, a two-pace culturing process is assumed: after five days of proliferation of muscle stem cells, the bioreactor is tuckered and filled with a different medium for 72 h of jail cell differentiation and mass proceeds. It is assumed that the main constituents of the civilization media are peptides and amino acids from soy hydrolysis, glucose from corn starch, and again a negligible volume of growth factors. In contrast to the more speculative approach of the two papers above, this report bases its assumptions on the metabolic requirements and yields of cultured meat on data from Chinese Hamster Ovary (CHO) cell proliferation (Sung et al., 2004), as a previously tested analog for cell culture weather condition. Corn starch microcarrier beads provide a scaffold around which cells proliferate, and the procedure is assumed to accept place within stirred-tank bioreactors. Energy is required for aeration, mixing and temperature regulation during the civilisation phase. Finally, the bioreactors are cleaned between each culture batch by rinsing with sodium hydroxide and heating to 77.5°C. See Mattick et al. (2015b) for further details. As more than optimistic estimates were already demonstrated in the two papers above, the boilerplate cultured meat footprint was used rather than the depression end of the sensitivity analysis. This GHG footprint was 6.64 kg CO₂, 0.019 CH₄, and 0.0013 kg N₂O, giving a full GWP₁₀₀ footprint of 7.5 kg CO₂e per kg cultured meat (disaggregated emissions from Carolyn Mattick, pers. comm.).

To represent the upper stop of proposed emissions footprints for cultured meat product, the event from the high finish of the sensitivity analysis in Mattick et al. (2015b) was also used. Here, lower cell densities are achieved at the end of the proliferation phase, no further biomass growth is achieved in the differentiation phase, and the biomanufacturing facility building size and free energy footprint are treated as comparable to a pharmaceutical found, rather than a brewery as in the default scenario. This resulted in a footprint of 25 kg CO₂east per kg cultured meat. It was not possible to extract the individual gas composition from the sensitivity analysis, but for this study we assume that the gases constitute the same proportions as in the baseline case, resulting in 22.1 kg CO₂, 0.062 CH₄, and 0.0043 kg Due north₂O per kg cultured meat.

A further emissions footprint for cultured meat is as well provided by Smetana et al. (2015), but as some details regarding the functional unit, organisation boundaries and production methods assumed in this study were unclear, and the carbon dioxide equivalent footprint presented was similar to the result at the loftier end of the sensitivity analysis in Mattick et al. (2015b), information technology was not used in this study.

Three representative beef footprints were used post-obit Pierrehumbert and Eshel (2015) to illustrate some of the variation in quantity and limerick of emissions associated with contemporary beef product systems (Table 1). The lowest footprint for all gases is demonstrated by product at an organic Swedish ranch from Cederberg and Nillson (2004). This is an extensive, low-input (no pesticides or constructed fertilizers, but organic squealer manure imported) arrangement that achieves birth rates of approximately one fauna a year and fast weight gain, hence low methane emissions per output. An culling footprint composition is shown in the Brazilian pasture arrangement from Cederberg et al. (2009), which is besides an all-encompassing, low-input system, but methane emissions per unit beef produced are significantly greater due to slower creature weight proceeds. CO₂ emissions from production are likely actually lower than in the Swedish case (rather than equal, equally shown in the table) as this footprint includes emissions resulting ship from Brazil to Europe; however, these are more than start by likely emissions resulting from deforestation, which are not included here just returned to in the discussion. Finally, the highest beef footprint included is a pasture arrangement in the Midwestern United states of america from Pelletier et al. (2010). This organization also achieves relatively fast beast weight gain, and so methyl hydride emissions are equivalent to the Swedish organization, merely this is achieved through an free energy and input intensive management that results in loftier carbon dioxide and nitrous oxide emissions. For further details see Pierrehumbert and Eshel (2015) and the original studies referenced. Two further footprints demonstrating emissions from a Midwestern Usa feedlot and the average for Swedish beef product included in Pierrehumbert and Eshel (2015) were omitted from this study for clarity, as they provided intermediate emission profiles that were like to those described above.

Table ane. Emissions profiles of cultured meat and beef cattle product, expressed as private gases and total IPCC 5th Assessment Study 100-Years Global Warming Potential carbon dioxide equivalent (GWP₁₀₀ CO₂e) per kg of meat output (either cultured meat or os gratuitous beef).

As these beef footprints are not completely harmonized (e.thousand., the emissions incurred in the transport of Brazilian beef to Europe noted above), the emissions described for each system may stand for methodological differences betwixt studies, such equally different organization boundaries, co-product allocations and LCA databases, rather than differences between the beef production systems themselves. Comparing individual LCA studies tin can exist problematic, even for the same product (de Vries et al., 2015), and there are meaning challenges in standardizing agricultural LCAs (Adewale et al., 2018). For the purposes of this study, these footprints provide contrasting case-studies with a different balance of GHG emissions to illustrate the distinct climate impacts of each gas, only should not necessarily be taken every bit globally representative or definitive, standardized beef LCAs.

Emissions footprints for every system are shown in Table one. Information technology should exist noted that all cultured meat carbon dioxide equivalent footprint estimates, including the high end of the sensitivity analysis, are lower than those of every cattle system in this report.

Consumption Pathways

Three alternative consumption pathways were used to illustrate the dynamics resulting from the alternative GHG footprints, with impacts from all systems shown for i,000 years.

The first scenario is based on constant, very high levels of meat consumption: 25 kg per capita per annum (roughly the contemporary beef consumption charge per unit in the USA) for a population of 10 billion. This pathway is intended to explore the temperature impacts of unrestrained consumption and illustrate the singled-out climate impacts of different greenhouse gases under sustained emissions. (Notation that hither and for all other scenarios, we only model aggregated global totals, and the consumption described is causeless to atomic number 82 directly to the associated production (and hence emissions). Nosotros practise not accost issues surrounding, for instance, food waste, access, and distribution, despite their importance in designing a sustainable food system (Garnett, 2013), equally our focus is on demonstrating the relevant climatic principles).

The second scenario assumes the same very high consumption rates for the first 100 years, followed by an exponential refuse, i.eastward., consumption is a office of fourth dimension C(t) such that:

$\begin{array}{rc}C(t)=C_m\text{ if}t\le t_{\mathrm{one\; thousand}},& (1)\end{array}$

$\begin{array}{rc}C(t)=C_k{e}^{-(t-t_{\mathrm{thousand}})/\tau }\text{ if}t>t_m& (\mathrm{two})\end{array}$

where C _grand is the tiptop (and in this scenario, as well initial) consumption charge per unit, which declines after fourth dimension t _m (= 100 years) with fourth dimension constant, τ = 50 years. This scenario illustrates the difference between long-term warming impacts of each gas when their emissions turn down toward 0.

The tertiary scenario presents a more realistic sit-in and attempts to illustrate a potentially sustainable infinite for meat consumption. Meat consumption starts at a rate approximately equal to current global consumption (5.55 kg per capita per annum for a population of 7.three billion, post-obit Pierrehumbert and Eshel, 2015), and so increases exponentially to accomplish a peak consumption rate of 25 kg per capita per annum for a population of x billion after 100 years. Post-obit this peak, consumption declines exponentially to a long-term annual consumption charge per unit (C _∞) equivalent to 75% of current global consumption. Beef consumption is therefore defined as:

$\begin{array}{rc}C(t)=C_k{e}^{-{(t-t_m)}^2/{\delta }^2}\text{ if}t\le t_m,& (\mathrm{iii})\end{array}$

$\begin{array}{rcl}C(t)=& \mathrm{\text{max}}(C_{\infty },C_m{e}^{-{(t-t_{\mathrm{chiliad}})}^2/{\delta }^2})\text{ if}t>t_k& (4)\end{array}$

where C _k is again the peak consumption charge per unit, occurring in this case at time t _thousand (again 100 years here), reached at a charge per unit governed by δ, where $\delta =t_{\mathrm{one\; thousand}}{(ln\left(\frac{C_m}{C_0}\right))}^{-0.5}$ such that the initial consumption rate, C ₀ is every bit described above.

Climate Modeling Arroyo

Temperature responses were derived using an energy-balance climate modeling approach post-obit Pierrehumbert and Eshel (2015). Almanac emissions of each gas, as determined past the system type and consumption trajectories described above, are used to determine the change in radiative forcing and consequently warming over time.

Carbon dioxide forcing was calculated using a function that models change in atmospheric concentration of CO_ii, incorporating ocean uptake, and a logarithmic relationship betwixt changes in CO₂ concentration and resultant forcing (following Pierrehumbert, 2014). For CH_iv and N₂O, atmospheric concentrations were calculated assuming the gases persist in the atmosphere for 12 and 114 years, respectively, with forcing derived from these concentrations using linearized radiative efficiency coefficients from Forster et al. (2007). For CH₄ this forcing was increased by a factor of 1.45 to incorporate stratospheric water vapor distension and positive ozone feedbacks.

The transient energy balance climate model presented in Pierrehumbert (2014) was used to calculate warming resulting from these changes in forcing. A two-box body of water system is used whereby a shallow, mixed bounding main layer warms quickly (within years) in response to changes in forcing, just the deep ocean is warmed (through this mixed layer) on a much longer timescale. This two-box ocean system has the important effect of adding a delayed warming response, which can besides result in some connected warming even when forcing is stable or declining (Held et al., 2010). An equilibrium climate sensitivity of 3 K per doubling in the atmospheric concentration of CO₂ and a short-term transient climate sensitivity 2/3 of the equilibrium sensitivity were assumed. All climate model outputs are provided in a Supplementary Tabular array in addition to being illustrated in the results section below.

Results

The first consumption pathway, continuous consumption at very high rates (Figure ane) illustrates the scale of warming that would upshot from big-scale meat production from current beefiness cattle or hypothesized cultured meat systems. This scenario also demonstrates the distinct climate impacts of each gas. As illustrated for the warming resulting from each gas in the Brazilian pasture system (Figure 1A), at that place is immediate, significant warming from CH₄, merely under sustained emission rates this largely stops increasing later on a few decades (by this point the atmospheric concentration of CH₄ has reached an equilibrium, and hence the forcing it results in remains the same, but there is all the same a slight long-term increment in warming due to the pregnant time lag for the temperature response of the deep ocean). This equilibrating dynamic is likewise observed for N₂O, simply on a calibration of a few centuries rather than a few decades. In contrast, as a significant proportion of CO_two emissions persist indefinitely, no equilibrium forcing is reached for this gas, and hence warming continues to increase for every bit long equally emissions are sustained. These dynamics are illustrated very strongly past comparing cattle to a cultured meat production system (Figure 1B). Cultured meat emissions of CH₄ and North₂O are relatively pocket-size and and then do non significantly contribute to overall warming dynamics; instead we see a long-term perpetual increase in warming driven largely past the rate of on-going CO₂ emissions.

Figure ane. Warming touch on for perpetual consumption at very high rates (250 Mt per year) for beef cattle and cultured meat production systems for 1,000 years. (A,B) illustrate the individual and combined warming impact of separate greenhouse gases for representative beefiness cattle (A) and cultured (B) systems. (C–E) show total warming impacts for all systems.

The wider organisation comparisons provide further demonstrations of these dynamics. Amidst the beefiness cattle production systems (Figure 1C), the Mid-Western Us pasture organisation shows a much greater degree of long-term warming than the Brazilian organization, despite only a marginally higher carbon dioxide equivalent footprint, due to the greater proportion of CO₂. The Swedish ranch organisation compares favorably to both, every bit the CO_ii component is depression and hence we run across limited long-term increase in warming, merely due to greater production efficiency than the Brazilian system, CH₄ (and N₂O) emissions are also lower, and hence the forcing that results in one case atmospheric concentrations accomplish equilibrium is less. Among the cultured meat product systems (Figure 1D), the warming is driven largely (or entirely for "cultured-a" and "-b") by CO₂ emissions, and so at that place is perpetually increasing warming, the slope of which depends on the charge per unit of annual CO₂ emissions. Despite concerns over the potential omission of some CH₄ and N₂O emissions in the cultured-a and -b footprints as noted above, the marginal impact of these gases for cultured-c, where these information were available, suggests that overall trends would exist similar.

Bringing all system types together (Figure 1E) nosotros see that the ii most optimistic cultured meat footprints, cultured-a and cultured-b, are sufficiently modest that these systems do indeed have a lesser climate touch than cattle systems. These two cultured meat systems remain superior to even the best beef cattle production organization into the very long term (one,000 years), although their relative advantage declines over time and past the end of the period modeled is significantly less than might exist implied by comparing carbon dioxide equivalent footprints (cultured-a footprint = 1.69 kg CO_iidue east kg⁻¹ meat, Swedish = 28.half dozen; but by t = i,000 the temperature impacts are +0.xviii and +0.62 One thousand, respectively). The about hitting instance of these dynamics is provided by cultured-d, the production scenario at the high-stop of the sensitivity analysis in Mattick et al. (2015b). Despite having a lower carbon dioxide equivalent footprint that all cattle systems here, within 200 years of continued production the Swedish system is superior, and by 450 years is outperformed by fifty-fifty the worst cattle system here (despite having only 57% of its carbon dioxide equivalent footprint). This system is so increasingly outperformed by all of the cattle systems the longer that product is maintained.

An alternative aspect of the unlike temporal dynamics of each gas is revealed by the scenarios in which production declines toward zero subsequently 100 years, every bit shown in Figure 2. One time emissions of CH₄ and N₂O terminate the warming these emissions resulted in is reversed over timescales largely dependent on the atmospheric lifespan of each gas (Figure 2A). In dissimilarity, the warming due to CO₂ is not reversible within the timescales modeled here, and so warming acquired past CO₂ persists (shown more clearly in Figure 2B). Every bit a event, while the warming from cattle (Figure 2C) systems declines, the warming from cultured meat production persists indefinitely at a fixed level based on the cumulative CO_ii emissions accrued upwardly to the point at which production ceases (Figure 2D).

Figure two. Warming bear on for consumption at very high rates (250 Mt per twelvemonth) followed by a refuse to aught for beef cattle and cultured meat product systems for 1,000 years. (A,B) illustrate the private and combined warming impact of separate greenhouse gases for representative beefiness cattle (A) and cultured (B) systems. (C–E) show full warming impacts for all systems.

The potentially more realistic scenario of an increase in consumption followed by a refuse to more sustainable levels is shown in Figure iii. For the Brazilian beef cattle systems (Figure 3A), the warming resulting from CH_iv and N₂O grows rapidly in line-with increasing production, only then stabilizes at a new, lower level responding to the new emissions rates. For CO₂, still (again shown more clearly in the cultured meat example, Effigy 3B), the reduction in emissions rate slows the charge per unit of further warming, but this is added to the warming caused by historical emissions, which persists. The overall consequences of these dynamics depend on our climate objectives. The cattle production systems evidence greater pinnacle warming within this time-frame (except for the comparison between the Swedish system and the highest footprint cultured meat system), just equally a outcome of the persistence of the big-scale CO₂ emissions in the early periods of product for cultured meat, any long-term benefits of this production are further reduced compared to cattle systems.

Effigy 3. Warming impact for consumption at very high rates (250 Mt per year) followed by a pass up to cipher for beef cattle and cultured meat production systems for 1,000 years. (A,B) illustrate the private and combined warming impact of dissever greenhouse gases for representative beefiness cattle (A) and cultured (B) systems. (C–Due east) prove total warming impacts for all systems.

Discussion

As originally stated in Pierrehumbert and Eshel (2015), the temperature impacts of very large levels of beef consumption, under whatsoever of the systems explored here, are pregnant and probable incompatible with our climate goals. Despite the bold claims and superior carbon dioxide equivalent footprints, yet, cultured meat is not necessarily a more sustainable alternative. In the most optimistic cultured meat production footprints, emissions are competitive with cattle systems for CO_two while avoiding the other gases: this is unambiguously superior from a climate perspective. Even so, the long-term advantage over cattle is non as dramatic as may exist suggested by simple GWP₁₀₀ comparisons. For the almost conservative cultured meat footprint used here, which still had a lower carbon dioxide equivalent footprint than any cattle system in the study, the long-term temperature impact of production is dramatically worse than any cattle system. Furthermore, equally emissions from cultured meat are predominantly composed of CO₂, their warming legacy persists fifty-fifty if product declines or ceases (in the absenteeism of active removal of this CO₂ from the atmosphere). Replacing cattle systems with cultured meat production before energy generation is sufficiently decarbonized and/or the more than optimistic production footprints presented here are realized (assuming they can be), could risk a long-term, negative climate affect.

In this study, beef was selected as the livestock meat to compare with cultured systems due to its particularly high carbon dioxide equivalent footprint. It is hitting how poorly these footprints stand for to long-term temperature affect, indicating the pregnant influence of the unlike atmospheric lifespan of each gas not adequately captured by the GWP₁₀₀ metric. The 100-years time-frame demonstrates the increasing divergence between GWP₁₀₀ footprints and warming bear on, just the relative exaggeration of the impacts of sustained methane emissions is apparent well before this (whatever period across 100 years). GWP₁₀₀ CO₂ equivalents as well fail to highlight some of the significant shorter-term differences between marsh gas and CO_two, neither reflecting the firsthand (within ~20 years) large-calibration impacts of initially increasing methane emissions nor capturing the reversal of warming resulting from decreasing (or halting) emissions (which is also the instance for nitrous oxide in the longer-term).

As on-going emissions of short-lived gases such as methane behave so differently to CO₂, even over immediate, policy-relevant timescales, we need to consider alternative appraisals for activities where emissions are largely composed of methane: here, cattle production, but other biogenic sources such equally rice production, or fossil fuel sources such as natural gas leakage would need to consider similar dynamics. Information technology is not sufficient to make broad climate claims based on GWP₁₀₀ carbon dioxide equivalent footprints lone. In order to investigate these bug, emissions associated with an activity must be provided in a disaggregated class allowing the assessment of each gas, yet these data are non mostly available at present, and nosotros urge researchers to provide them in the future (Lynch, 2019).

Information technology has been argued that as the emissions from cultured meat are primarily from energy use, they may be significantly reduced in the futurity if energy generation is decoupled from emissions (Tuomisto and Teixeira de Mattos, 2011)—and given the long timeframe used here, large scale energy decarbonization will be essential well within this period to prevent very significant climate impacts irrespective of whatever emissions associated with food production. In the to the lowest degree optimistic cultured meat scenario here, however, the magnitude of energy required is such that sufficient decarbonized energy generation appears unlikely in the most to medium term. Assuming an energy footprint of approximately 360 MJ per kg cultured meat (high-terminate of the sensitivity analysis in Mattick et al., 2015b), the product of 25 kg per capita per annum for a global population of 10 billion would require around xc EJ energy per annum, 22.9% of the 393 EJ total global energy consumption in 2015 (International Energy Bureau, 2017); hence unrestrained consumption would consequence in a pregnant proportion of global energy supply going toward growing lab-grown meat in the absence of low-energy product systems.

Decarbonized free energy generation would also eliminate a proportion of the CO₂ emissions from cattle systems, so for this analysis we used footprints every bit presented under contemporary energy emissions assumptions. Additionally, the timing of a big-calibration decarbonization of energy generation would have significant impacts on wider climate targets, including determining the extent of on-going methane emissions that are uniform with a given temperature ceiling. As cultured meat is an emerging technology, wider improvements in efficiency of production may reduce its emissions footprint in the futurity, in improver to the decarbonization of energy generation. This, too, could as well utilise to cattle systems though, employing mitigations or technologies or moving to more efficient systems (Rivera-Ferre et al., 2016).

Indeed, it could be argued that comparing extant cattle production with hypothesized cultured meat systems presents a biased parallel. The speculative nature of all 4 cultured meat footprints tested here is borne of necessity, as to date there are no LCA of actual cultured meat production (at least in the public domain), despite manufacturer claims that a commercial launch is imminent (Stephens et al., 2018). Given the unknowns in this new form of production, we must exist aware that impact assessments may change, and continue to take a systematic approach (Mattick et al., 2015a). There is a need for much greater transparency from cultured meat manufacturers, with relevant data available to interrogate any environmental claims.

In addition to the broad nature of each footprint, some specific elements of the cultured meat LCA remain unclear due to their speculative nature. In the default approaches from Tuomisto and Teixeira de Mattos (2011), for example, a proportion of emissions incurred in the production of cyanobacteria are not allocated to cultured meat, instead presumed assigned to food supplements. The potential for whatsoever co-products from cultured meat production will depend on the systems that might be realized. They should besides exist handled similarly to whatsoever co-products from cattle production, such as leather; only the handling of livestock co-products in LCAs tin be complex, and is non well-standardized at present (Mackenzie et al., 2017).

The nature of the functional unit—the unit of output to which emissions are assigned—also remains speculative in the case of cultured meat. If protein rather than "meat" was taken as our functional output the footprints would testify even greater differences betwixt studies, with Mattick et al. (2015b) assuming 7% protein by weight, compared to 19% in Tuomisto and Teixeira de Mattos (2011) and Tuomisto et al. (2014). Comparing impacts on a per protein (or wider nutritional) basis will exist important as more than detailed and/or real product footprints go available. Fifty-fifty with a generic meat functional unit, as used in this report, there may still be further differences not captured hither. In Mattick et al. (2015b) the functional unit of measurement is 1 kg of cell biomass: any farther processing or additional ingredients required to convert this biomass into an edible course or a conventional meat product analog would also need to be included for a full life bicycle cess comparing last meat products. Tuomisto and Teixeira de Mattos (2011) assumed their cultured meat system output is a "minced-beefiness type of product," only may still differ from cattle beef in nutritional or sensory attributes, with farther processing (and hence steps to consider in a life bike assessment) potentially required if a complete beef analog is sought. The impacts of whatsoever processes to produce dissimilar meat products, such as steaks, may be even greater, and more circuitous tissue applied science of this type is not anticipated in the almost-future (Stephens et al., 2018). Processing of livestock products can also be associated with considerable emissions (Poore and Nemecek, 2018), and so organization boundaries must consistently include these in future piece of work comparing ecology impacts of final products ready for consumption.

Spared land-utilize has been presented as another significant reward of cultured meat production (Tuomisto and Teixeira de Mattos, 2011), and this land could entail a further climate benefit by existence used for carbon sequestration. This may also be a factor in improved cattle production withal, including simply more than efficient use of current grasslands (Godde et al., 2018). State-apply associated carbon fluxes are oft poorly standardized in agricultural footprinting approaches (Adewale et al., 2018), and were excluded here. These country-use carbon fluxes may have significant impacts. For example, pregnant deforestation has resulted from pasture expansion, and including the CO₂ emissions resulting from this would greatly increase typical Brazilian beef footprints (Cederberg et al., 2011). At the same time, grassland soils contain significant quantities of organic carbon, and could potentially sequester even greater amounts under advisable management (Conant et al., 2017). Further detail and standardization in land-use emissions and sequestrations is required in the future, including an appraisal of likely culling land-uses post-obit sparing of current agronomical state.

Although this study is concerned with the climate impacts of meat production, a wider context must also exist considered. A number of other environmental impacts are associated with beef production, such as water pollution and acidification (Poore and Nemecek, 2018), and cultured meat may provide benefits in these wider impacts; only once again, circumspection should be advised until reliable LCAs are bachelor for actual production systems. Conversely, we must besides consider the wider benefits that might be provided from meat production systems, including associated co-products, the provision of ecosystem services, their socioeconomic role in rural communities, and their landscape or cultural value (Rodríguez-Ortega et al., 2014). It has been argued that cultured meat production is a potentially transformative engineering science, and so social assessments must also be made to anticipate the disruption (positive or negative) that may be acquired (Mattick et al., 2015c), aslope environmental impacts such as climatic change. As a concept, it has been suggested that cultured meat overcomes some of the ethical problems of livestock production (Schaefer and Savulescu, 2014), but has as well been criticized as a problematically techno-centric, profit-motivated approach (Metcalf, 2013). Hocquette (2016) questions the broad need for cultured meat, suggesting that at that place are already alternative solutions that nosotros could employ to overcome problems with our food system. Finally, any climatic or wider benefits that may be possible through replacing livestock systems with cultured meat depends on how people perceive and ultimately consume cultured meat products (i.e., as a direct replacement or in improver to conventional livestock products). Early on research suggests consumer reluctance to supersede conventional with cultured meat, with public willingness to swallow cultured meat dependent on a number of personal concerns and anticipated benefits (Bryant and Barnett, 2018).

Conclusions

The scale of cattle production required for the very high levels of beefiness consumption modeled here would result in significant global warming, but it is not yet clear whether cultured meat production would provide a more climatically sustainable alternative. The climate impacts of cultured meat production will depend on what level of decarbonized free energy generation can be achieved, and the specific environmental footprints of production. There is a demand for detailed and transparent LCA of real cultured meat production systems. Based on currently bachelor data, cultured production does not necessarily requite license for unrestrained meat consumption.

Author Contributions

JL and RP designed the study and carried out the modeling. The manuscript was written by both authors post-obit an initial draft by JL.

Funding

This research was funded past the Wellcome Trust, Our Planet Our Wellness (Livestock, Surroundings and People—Leap), laurels number 205212/Z/sixteen/Z.

Conflict of Interest Argument

The authors declare that the research was conducted in the absenteeism of whatever commercial or fiscal relationships that could be construed every bit a potential conflict of interest.

Acknowledgments

Thanks to Carolyn Mattick and Hanna Tuomisto for providing further details on their cultured meat life cycle assessments and providing feedback on the organization descriptions in this newspaper, and to Alexandra Sexton for helpful feedback and discussion. We would likewise similar to thank the 2 reviewers for their constructive comments.

Supplementary Material

The Supplementary Cloth for this commodity can be establish online at: https://www.frontiersin.org/articles/10.3389/fsufs.2019.00005/total#supplementary-material

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