Dialing Back the Doomsday Clock with Circular Bioeconomy

Abstract

Present day status of planet earth is perilous. In January 2023, the “Doomsday Clock” (a serving global indicator for worldwide catastrophe) crept up to 90 seconds before midnight. According to the bulletin of atomic scientists, the Doomsday Clock aims to designate humanity’s closeness to annihilation; with midnight being the instance of ignition and thus, the point of no return from Armageddon. Because 90 seconds is the closest the clock has ever been to midnight, the year 2023 is therefore, planet earth’s nearest to Armageddon. But why is planet earth perilously close to extinction? The bulletin of atomic scientists cited threats from War; Disease; Climate change; and Disruptive technologies as major contributors. In the context of climate change mitigation, this chapter attempts to present contributions of the circular bioeconomy paradigm that could help humanity to dial back the Doomsday Clock. Anaerobic digestion (AD), integrated regenerative agriculture (IRA), controlled ecological life support system (CELSS), bioregenerative life support system (BLSS), note by note cuisine (NNC), circularity, and molecular pharming are some of the solutions isolated.

1. Introduction

The “Doomsday Clock” is a construct of the bulletin of atomic scientists that serves as a barometer for humanity’s nearness to irreparable destruction. Midnight hour on the clock is designated to be the instance of ignition and thus, the point of no return from disaster. On 24th January 2023, the Doomsday Clock got to 90 seconds before midnight. This was the closest the clock had ever been to humanity’s insertion into the extinction process. Analyses by the bulletin of atomic scientists indicated that the threats of war (biological, chemical, nuclear); disease (zoonotic epidemics and pandemics); climate change (weather extremes such as radical storms and heat waves); and disruptive technologies (cyber space, drones, artificial intelligence, social media) are major contributors. These contributors were also indicted in the Stanford existential risk initiative (SERI) study [1]. Luckily, several of these factors are amenable to anthropogenic interventions. But are humans doing enough to prevent the progression of Doomsday Clock to the point of no return (aka Armageddon)? Would humanity mobilize all that it may take (cooperation, technology, political resolve and courage, and any other resource needed) to constrain anthropogenic polluting emissions, attenuate the exceedance of planetary boundaries, and forestall irreversible perturbation of the earth’s system? This chapter proffers mitigation strategies for climate change. Specifically, climate change attenuating applications of biomass resources as indicators of the circular bioeconomy model that could help humanity to dial back the Doomsday Clock are presented.

2. Signatures of climate change

Climate change may manifest in weather extremes: floods, torrential rainfalls, radical storms, cold spells, heatwaves, severe droughts, and wildfires. These events could cost life; destroy residential and commercial buildings, public utilities, and infrastructures; lead to contamination of natural resources (e.g., air, soil, and water bodies); disrupt numerous functions including schools; social events; air, land, and sea transportation.

2.1 Storms, rainfalls, and floods

Drastic storms like cyclones, hurricanes, tornados, and typhoons may encompass blizzards, hail, rain, snow, lightning, thunder, and strong winds. As shown in Figure 1, the outcome could be devastating for communities in technologically advanced and developing nations alike.

• In 2016, a flood impacted households in Sri Lanka. A case study of extreme weather events revealed that about 55% of households surveyed in a rural community were exposed to the 2016 flood event [6].

• In 2020, land use influences and heavy rains caused Lake Victoria to rise by >1 m. Trigged floods submerged jetties in Uganda [7]. The rains, the worst in 19 years, affected most of sub-Saharan Africa above 10^oS [8].

• The July 2021 flood in Europe impacted schools, public utilities, and the health system. Bridges, motorways, railway lines, clinics, hospitals, and pharmacies were damaged and over 220 people died [2].

• In 2022, heavy rains caused flooding in West Africa. Nigeria and Niger in June; Chad in July; Cameroon in August; and Benin in September. Over 4.6 million people were affected with at least 829 killed [9].

• In 2022, unsafe storms from the Indian Ocean visited Southeastern Africa. Winds, rains, and floods impacted Madagascar, Mozambique, and Malawi. Deaths and infrastructure destruction were recorded [5, 10].

• In 2022, extraordinary heavy rainfall hit vulnerable communities in Northeast Brazilian states, generating flash floods and landslides. Over 25,000 persons were displaced and at least 133 fatalities were reported [11].

• In June 2022, extreme monsoon rainfall unleashed floods and landslides in Pakistan. As of 9th September 2022, reported impacts included over 33 million people affected, and 1396 deaths [12, 13].

• In December 2022/January-February 2023, atmospheric rivers and storms hit California State in the USA. Ensued ruins of infrastructures and communities were reported with several photos (Figures 1D and E [4]).

Figure 1.

Effects of storms, rains, and floods on planet earth. Photo sources. (A): Joe Raedle/Getty Images: Residents of Houston evacuate their homes after the area was flooded from Hurricane Harvey, – Yahoo Image Search Results (Accessed 1st June 2023); (B): [2]; (C): [3]; (D and E): [4]; and (F): [5].

2.2 Cold and heat extremes

Cold and heat extremes disrupt energy facilities, food supplies, economic activities, and endanger humans, plants, and animals. Impacts of non-optimal temperatures have been reported [14, 15]; and are stressed by age, comorbidities of health condition, gender, race, socioeconomic status, and pharmaceuticals. For example, medications that impair thermoregulation or depress sweat gland functions have been implicated [16].

2.3 Severe droughts

Drought is a key constraint affecting food supply, especially in areas dependent on rain-fed agriculture. Water stress impedes water bodies, food, and forage crops. Livestock grazing/production, lakes, and ponds become devastated (Figure 2), exacerbating the economic status and welfare of subsistence farmers and households.

Figure 2.

Impacts of drought on planet earth. The remains of dead livestock and a donkey (left), and cracked earth in an area once under the water of a Lake. Source: [3].

2.4 Excessive wildfires

Figure 3 presents sites that are becoming rather common on planet earth. From country to country, wildfires have been occurring with alacrity. Brazil, Greece, Indonesia, Italy, Portugal, and Spain are among the victims in recent years. Wildfires destroy human life, and rare plant and animal species; and emit heat energy, smoke, carbon monoxide (CO), and other pollutants with adverse environmental and health effects. The wildfires of 2019–2020 in Australia aggravated health issues, caused 417 deaths, and emitted about 715 Tg CO₂ [19, 20]. In February 2023, the searing heat wave in the Parana-La Plata Basin, Chile, caused flames to spread, killed over 20 persons, injured over 1000 others, and burnt about 270,000 hectares of land [21]. In early June 2023, various news channels were reporting the fallout of wildfires from Canada (Figure 3B) that affected several states in the USA; including New Jersey, New York, Pennsylvania, and Washington DC; the nation’s capital. Some air flights were interrupted, schools closed, Broadway shows canceled, and residents were urged to stay indoors, and/or wear masks [NPR news bulletin of 8th June 2023]. By mid-August 2023, the Maui Hawaii wildfires in the USA had traumatized families, erased homes, devastated infrastructures, killed over 100 persons, and hundreds more reported missing [CBS and BBC news bulletins of 16th August 2023].

Figure 3.

Excessive wildfires cause destruction and pollution on planet earth. (A): Raging wildfires. Source- Munich Re; https://www.munichre.com/natcatservice (Accessed 26th February 2023). (B): Wildfires smoke aerosol over Zama City, Alberta, Canada. Source: Alberta Wildfire/Handout via Reuters [17]. (C): Smoke pollution over the Pacific Ocean. Source: [18].

3. Who (or what) is to be blamed?

Who or what causes breaches of planetary boundaries that trigger climate change? Some authors have blamed natural phenomena. Solar proton events inject nitrogen oxides that destroy ozone in the stratosphere [22]. In 2010, natural aerosols affected the global energy balance more than anthropogenic aerosols [23]. In 2021, the amount of sulfur dioxide (SO₂) emitted into the troposphere by the La Palma volcanic eruption (≈ 1.8 Tg), exceeded the total anthropogenic SO₂ emitted from the 27 European Union countries in 2019 [24]. Thundercloud coronas may be a major source of greenhouse gases [25]. Other authors assert anthropogenic activities are culpable [9, 26, 27, 28]. A classic example that illustrates this dichotomy surrounds the extremely hot summer of 2010 in Russia. One group of scientists concluded that the intense heatwave was mainly due to nature [29]. Another group, with 80% probability blamed human influences [30]. The same event with different determinations that may be both right? [31]. Yet other researchers surmise that natural and human activities are both contributors, with the human inputs perhaps more pronounced in the Anthropocene epoch [8, 32, 33]. Irrespective of the force (human or natural), extreme events may be key indicators of climate change, and environmental responses to its perturbations, such as the effects on glaciers [34, 35]. It also appears that climate change could be precipitated and driven by greenhouse gases and aerosols. A question may be asked, what are the anthropogenic emanators of these drivers, and what strategies might be deployed to mitigate them? If the natural contributors to climate change cannot be controlled, it is imperative or rather obligatory that human-made causes be attenuated.

4. Causes of climate change

Climate change seems to be generally forced by greenhouse gases and aerosols. If so, then, what are these so-called greenhouse gases and aerosols that pollute the environment and influence the climate?

4.1 Greenhouse gases

To maintain earth’s radiation budget, the radiant energy coming from the sun must be in a fair balance with the radiation leaving the earth. If the emission from earth falls short, energy would accumulate and force the earth’s temperature to rise. There are gases in the atmosphere that absorb and prevent the radiation emitted by the earth from escaping into outer space. The energy trapped by these gases is radiated back to earth, causing the earth’s temperature to warm up. Gases with this ability are called greenhouse gases (GHGs). GHGs include Carbon dioxide (CO₂), Methane (CH₄), Nitrous oxide (N₂O), and Halocarbons. GHGs do occur naturally. But a group of halocarbons that contain fluorine, known as Fluorinated gases (F-gases), are mostly human-generated. F-gases include sulfur hexafluoride (SF₆) used as an insulating gas, and for the production of aluminum and magnesium; hydrofluorocarbons (HFCs) used as blowing agents and refrigerants; and perfluorocarbons (PFCs) used in the electronics industry for semiconductor manufacture. F-gases are potent GHGs that contribute significantly to climate change [36, 37]. Table 1 highlights the characters of some GHGs.

S/N	GHG	Concentration (mol/mol)	Lifetime (Years)	Radiative forcing (W/m^2)	Global warming potential; (100 years)*
1	Carbon dioxide (CO2)	365–409 × 10^−6	≈100	1.66	1
2	Methane (CH4)	1.7–1.857 × 10^−6	10–12.4	0.48	25
3	Nitrous oxide (N2O)	319–331 × 10^−9	114–131	0.16	298–320
4	Chlorofluorocarbon (CFC-12)	538 × 10^−12	102	0.17	8500
5	Sulfur hexafluoride (SF6)	5.6–9.6 × 10^−12	3200	0.0029	22,800–24,900
6	Perfluoromethane (CF4)	74–79 × 10^−12	50,000	0.0034	6300–7390

Table 1.

Characteristics of some greenhouse gases.

*

Relative to CO₂.

Source: Compiled from [27, 36, 38, 39, 40].

4.2 Aerosols

Air quality may be eroded by particulates. Particles of public health attention are defined by an aerodynamic diameter in the range of ≤10 μm (PM₁₀). Fragments with diameters less than 2.5 μm (PM_2.5) are identified as fine particles. Aerosol is the technical parlance used to denote airborne liquid and solid droplets and particles. Aerosols are ever-present (inside/outside homes, buildings, atmosphere); could be of human or natural origin; primary (when emitted directly from pollution sources) or secondary (when made from precursor pollutants); and could exhibit greenhouse gas properties or function as reflectors. Aerosols include sulfates (SO₄²⁻), nitrates (NO₃⁻), black carbon (BC), and a plethora of other compounds, and chemical species [41, 42]. Examples of natural aerosols are desert dust, sea salt particles, meteoritic fragments, as well as ash and sulfates from volcanic eruptions. Aerosols affect atmospheric and ocean conditions including cloud droplets, circulation, snow covers, precipitation, temperature, and heat transfer; thereby influencing planetary energy and water budgets [18, 26]; and the references in these citations. Those aerosols that absorb radiation from the sun (e.g., BC, mineral dust) could fulfill the effects of GHGs and warm the earth, while those that reflect and scatter radiant energy (e.g., SO₄²⁻, NO₃⁻) may impart cooling effect. Collectively and on average, aerosols appear to have a net cooling impact [18]. In 2007, the solar direct radiative effect (DRE) for aerosols estimated from satellite remote sensing studies was reported to be −5.4 ± 0.9 W/m² [40]. The possible properties of some aerosols are presented in Table 2, and their pollution impacts exhibited in Figure 3.

S/N	Aerosol	Diameter (μm)	Concentration (μg m^−3)	Lifetime (Days)	Radiative forcing (W/m^2)
1	Black carbon (BC)	2.5	0.10–0.63	1.8–15	0.002–5.335
2	Organic carbon (OC)/Particulate organic matter (POM)	2.5	(3.0 ± 0.6) to (191.2 ± 104.3)	4.3–11	(−0.31) to (−0.09)
3	Nitrate (NO3^−)	2.5–192	0.72–84.24	0.8–25	(−0.17) to (−0.03)
4	Sulfate (SO4^2−)	8.0–30.6	0.1–50.0	2.3–5.2	(−1.5) to (−0.96)
5	Dust	0.01–100	0.3–180	1.3–7	(−0.56) to (+0.1)
6	Ammonium (NH4^+)	2.5–192	0.56–43.68	4–6	(−0.11) to (+0.21)

Table 2.

Potential characteristics of aerosol pollutants.

Source: Assembled from [18, 40, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57].

5. Anthropogenic sources of the breaches and exceedances of planetary boundaries

The major anthropogenic GHGs breaching planetary boundaries and perturbing the global climate system are CO₂, CH₄, N₂O, and F-gases. Their percentage repartitions to the global GHG budget are estimated at 72–76% for CO₂, 16–19% for CH₄, 6% for N₂O, and 2–3% for F-gases [58, 59]. The major aerosols include BC, organic carbon (OC), SO₄²⁻, and NO₃⁻. BC and OC are primary aerosols because they are emitted directly from pollution sources, while SO₄²⁻ and NO₃⁻ are secondary aerosols given that they are generated from precursor pollutants. The F-gases are totally anthropogenic, and their industrial applications are highlighted in Section 4.1. Anthropogenic sources of the other GHGs, primary aerosols, and precursor pollutants are intricately tied to humanity’s methods of exploitation of fossil and biomass energy resources. Their three main sources are:

1. Fossil fuel: For example, coal, crude oil (also known as oil or petroleum), and natural gas. Emissions arise from their production, combustion, and use, including flaring.

2. Biofuel: Such as wood, charcoal, dung, bioethanol, and biodiesel. In their production, combustion, and use, encompassing domestic and industrial applications.

3. Open biomass burning: Such as for shifting cultivation, combustion of agricultural waste, land use change, and permanent deforestation.

Global annual GHG emissions increased by about 57% between 1990 and 2018, from 32.7 to 51.2 Gt CO₂ eq, with the increment dominated by CO₂ emissions from fossil fuels. Anthropogenic CO₂ emissions declined from ≈ 37.7 Gt in 2018 to ≈ 36 Gt in 2020 [37]. Fossil energy CO₂ rose to 40.0 ± 2.9 GtCO₂ in 2021 [60], and in 2022 was reported to be about 36.8 Gt [61]. Anthropogenic share of global BC aerosol inventory in 2010 was reported as 66%. Those for precursor gases were 64%, 68%, and 83% respectively for nitrogen oxides (NOx = NO + NO₂), ammonia (NH₃), and sulfur oxides (SOx) [23]. The global percentage contribution of GHG emissions by the economic sector in year 2010 is shown in Table 3.

S/N	Economic sector	Share of GHG (%)
1	Energy: combustion of coal, natural gas, and oil, for heat and electricity generation (25%) fuel extraction, processing, refining, and conveyance (10%)	35
2	Agriculture: encompassing emissions from crop cultivation, livestock production, manure management, land use, land-use change, and forestry (e.g., deforestation, afforestation, population pressure), etc.	24
3	Industry: includes fossil fuels combustion at onsite facilities for industrial operations (e.g., chemical, metallurgical, and mineral transformation processes)	21
4	Transport: includes emissions generated by fuels combusted by mobile constructs as in aviation, marine (shipping, including boats in inland waterways), and terrestrial (e.g., rail, road, off-road/non-road) conveyances	14
5	Buildings: includes emissions from small-scale immobile facilities such as residential homes, and private and public offices.	6

Table 3.

Year 2010 distribution of global GHG emission by economic sector.

Source: Ref. [59].

6. Analysis of agriculture connections with exceedances of planetary boundaries

Table 3 indicates that agriculture is a major source of GHGs with a repartition of 24%. This share does not tell the whole story because GHGs do not all have equal impact on global warming potential (GWP). As Table 1 shows, on a one-hundred-year time horizon, CH₄ would exert 25 times the GWP of CO₂; and N₂O, 298 to 320 times. Hence impact of a sector on climate change is related not only to the ratio of GHG but also to the proportion and potency of constituent GHGs. Also, Table 3 did not disclose any information on the other climate forcer; aerosols. We will now take a closer look at agricultural connections with GHGs and aerosols.

6.1 Agriculture connections with GHGs

CO₂ captures the lion’s share of anthropogenic GHGs, accounting for ≈ 74% of the global ≈ 51.2 Gt CO₂ eq GHG emitted in 2018 [37]. Agriculture’s input to global CO₂ inventory is minimal, at 6–8% [62, 63]. In the USA in 2018, agriculture added just 0.63% of the over 5.4 Gt CO₂ inventoried [36]. On non-CO₂ GHGs, agriculture emits virtually no F-gases but is a huge emitter of CH₄ and N₂O. Estimates for CH₄ range from 31% [58] to 45% [64]; and for N₂O, from 66% [65] to 84% [62]. In 2005, agriculture emitted almost 54% of the non-CO₂ GHGs; 0% of the F-gases; about 45% of the CH₄; and over 82% of the N₂O (Author’s derivation, based on data in Table 3 of Ref. [66]). Agricultural CH₄ sources are livestock rumination (enteric fermentation), rice cultivation, manure management, and combustion of agricultural residues. Sources of N₂O are the burning of agricultural residues, synthetic fertilizer, manure, and soil management (nitrogen fixing, leaching/run-off, etc.).

6.2 Agriculture connections with aerosols

There are two major ways that agriculture contributes to aerosols and their effects. One is by direct generation of primary aerosols. The second mode is indirectly, by generation of precursor gases. Precursors can undergo chemical reactions that produce secondary aerosols and other GHGs. Incomplete combustion of agricultural biomass, and fossil fuels by agricultural machinery for example, liberates primary aerosols (BC, OC); precursor gases (CO, SO₂, NOx); as well as non-methane volatile organic compounds (NMVOCs) [42]. Precursors may also arise via manure management (e.g., NOx), fertilizer use (e.g., NH₃), and pesticide applications. In the aquatic ecosystem, pesticides were blamable for 81%, 87%, and 96% of the detected exceedances of the acute risk threshold (ART) related to fish, invertebrates, and algae, respectively [67].

6.3 Attribution assessment

Studies of tropical cyclones Ana and Batsirai that devastated Southeastern Africa deduced that human acts are at least in part liable for climate change. [9, 10, 28]. So did a study of the desert locust (Schistocerca gregaria) outbreak that impacted Ethiopia, Kenya, and Somalia [68, 69]. Anthropogenic GHGs are linked to energy and agricultural industries (Table 3). Agriculture is also a big aerosols emitter [48, 63, 70]. About 20% of the 3.3 million premature mortalities incurred in the world in 2010 from ozone and PM_2.5 pollution were attributed to agriculture [71]. A good amount of agriculture’s GHG and aerosol burden emanates from fertilizer manufacture and use. The Haber-Bosch fertilizer process via ammonia synthesis is a gargantuan fossil energy consumer and GHG emitter [72]. In the USA corn (maize) production system, for instance, baseline GHG emission is ≈ 2469 kg CO₂ eq per ha, and nitrogen fertilizer alone (manufacture and field losses) accounts for about 56% [73]. In livestock production, pig feed accounted for 79% of fossil fuel consumption and 88% of GHG emissions. The values for chicken feed were respectively 84% and 91%. In these studies, corn and soybean were basic inputs, and inorganic fertilizer was used in their cultivation [74]. In view of these values and recalling that nitrogen fertilizer and manure contribute 92% of all N₂O attributable to agriculture in the USA [75], and because fertilizer is required for the cultivation of maize and rapeseed, used for bioethanol and biodiesel creation respectively, a Nobel Laureate invested some computations. The results motivated the Nobel Laureate to caution that due to the larger GWP of N₂O relative to CO₂, and contingent upon the uptake efficiency of nitrogen fertilizer, the production of bioethanol from maize, and biodiesel from rapeseed, may lead to the emission of enough N₂O that wipes out the benefits of using biofuels to replace CO₂ emitting fossil fuels [76]. So, how may humanity manage and mitigate GHG emissions, to constrain climate change?

7. Circular bioeconomy to the rescue

The linear economic model operates on the norm of produce, use, and discard. Circular bioeconomy emulates nature’s edict of circularity (Chapter 6 in [77]; Fig. 2 in [78]; Fig. 1 in [79]; [80]; Fig. 5 in [81]; [82]). In the circular model, there is no waste. “Waste” from one process is “resource” and “input” for another. Circular bioeconomy was described as embracing wasteless design, and management tactics that recycle so-called wastes into useful goods [83, 84]. One study estimated the menace imposed by linear methods on nature’s worth at over one-half of global GDP (≈ US$44 trillion). The study also indicated that more than US$5.5 trillion in business opportunities and 163 million jobs could be generated by 2030 with the circular bioeconomy approach [84].

7.1 Approaches to achieving circular bioeconomy

Circular bioeconomy requires input from all stakeholders, including those that risk their well-being to put out wildfires and rescue flood victims. CO₂ is a major GHG tied to energy use, and agriculture is a major GHG and aerosol generator, via inorganic fertilizer use. Thus, decarbonization of energy systems and another fertilizer source are necessary. Approaches advocated here obligate renewable energy and the concept of integrated regenerative agriculture (IRA). Renewable energy [85], encompasses a broad gamut of energy carrier types, technologies, and names such as bioenergy [86], biofuels [87], biogas [88], biomass [89], biomethane [90], hydro [91], solar [92], wind [93], and several others. The work presented here highlights anaerobic digestion (AD) as the purveyor of renewable energy. This is because AD is perhaps the only current technology capable of addressing both issues of energy systems decarbonization, and substitution of ammonia-based fertilizer. In addition, AD will simultaneously address another issue threatening planet earth: waste management.

7.2 Anaerobic digestion (AD) technology

AD is a biochemical process that decomposes organic matter into flammable gas and nutritious watery sludge. The process occurs in a near oxygen-free environment with natural microorganisms. AD was probably recognized in a scientific sense about 392 years ago in 1630, when Jan Baptist van Helmont (1580–1644), observed that decomposing organic matter produced combustible gas; and during 1804–1808 John Dalton and Humphrey Davy established that the combustibility of the gas was due to the presence of methane [94, 95]. Today, AD is carried out within artificial environments named digesters, which are designed to optimize the process [96, 97, 98]. The combustible gas is called biogas, and the watery sludge, digestate. Biogas is composed of methane (40–75%), carbon dioxide (25–40%), and trace contaminants (≈ 0.1–3%). Digestate is rich in plant growth macronutrients; with their quantities and micronutrients contents related to the quality of the feedstock [98, 99]. Digestate attributes, AD’s technical feasibilities, types of feedstocks utilized (virtually all organic matter), limitations, advantages, benefits, applications, and much more have been presented in the literature [83, 96, 98, 100, 101, 102]. AD may be now considered a mature technology that could help humanity decarbonize industries, supplant inorganic fertilizers, and address waste management shortcomings.

7.3 Integrated regenerative agriculture (IRA)

IRA system combines food, feed, bioenergy, and livestock production in the farm space. IRA practices minimize the fuel/energy versus food mindset competition. The “this or that” image of pitting food production against energy production could be abrogated, thereby promoting synergy and coexistence of fuel, feed, and food cropping; enhancing carbon sequestration, and fostering sustainable ecological intensification. As of 2018, it was estimated that about 163 million farms in 100 countries, engaged 453 million hectares of agricultural land in some form of IRA [103]. The origin/history, definitions, lessons, modifications, and various aspects of IRA have been explored in published literature [104, 105, 106, 107]; tried, and/or implemented in several countries such as Colombia [108]; Italy [109]; Egypt [110]; Bangladesh [111]; USA [112]; Finland [113]; Chile and Vietnam [114]. Advocates argue that IRA would also enhance biodiversity, create wealth, support rural communities, improve the environment, increase equity, and mitigate injustice [84, 103, 115, 116, 117, 118]. Perhaps these reasons could invoke concern globally to justify a more stringent climate policy [119].

8. Implications of circular bioeconomy for the space food system

In low gravity, e.g., onboard spacecraft, and celestial body (Lunar-, Asteroid-) surfaces, providing food is more taxing than on earth. Humans operating in space face the dynamics of microgravity, radiation, and restricted activity [120, 121, 122]. In near-earth missions lasting days (Apollo, Space shuttle, Shenzhou), weeks (Skylab, Salyut), or even months (Mir, International space station, Tiangong space station), food could be carried at liftoff and resupplied from earth. Even in these cases, the space food system is mediated by biological, engineering, environmental, operational, and psycho-social factors. The specific constraints such as safety (biological); mass/volume (engineering); ergonomics (operational); and others have been discussed [122, 123, 124, 125, 126, 127, 128]; and detailed for the Apollo food system [129]. Longer durations and interplanetary destinations make food supply from earth onerous for various reasons. On cost for example, depending on the destination orbit, payload launch cost may range from $2719/kg for Falcon 9 launch destined to low earth orbit (LEO), to $28964.52/kg for Delta IV heavy launch destined to geosynchronous transfer orbit (GTO) [130]. Nevertheless, the performance of a launch system is governed by its mass fraction (ratio of the mass of propellants to the total mass of the launch system). The larger the mass fraction, the farther the destination and/or longer the duration. A larger rocket, such as the SpaceX Starship under development, would be able to carry more food, go farther, and last longer than the Saturn V rocket used for the Apollo moon program. But for a given launch system, the larger the food component of the payload, the nearer the destination and/or shorter the mission duration. With no infinite mass fraction launch system, onboard and in-situ food production become vital for successful long-time deep space missions, and extraterrestrial body habitations. To achieve this, space farming would need to benefit from circular bioeconomy technologies and concepts such as AD [131, 132, 133]; IRA [116, 134]; circularity [77, 78, 79, 80, 81, 82, 135]; bioregenerative life support system (BLSS) [136, 137]; controlled ecological life support system (CELSS) [138, 139, 140]; and note by note cuisine (NNC) [141, 142]. For greater plant utility and optimization, molecular pharming [143, 144] could be applied as well.

8.1 Sample study efforts on earth and in space

Research efforts have been expended both on earth and in space to ascertain the possibility of cultivating plant and animal food stocks in the space environment. Some examples are stated below.

• In Apollo quarantine tests of moon soil (regolith), a wide variety of biological species from the animal and plant kingdoms were utilized. Researchers [145, 146, 147] concluded that no microbe or harmful agents were found in the tested Apollo Luna regolith; some benefits could be associated with lunar soil cultivation; and that Lunar soil material is a potential source of nutrients for many plants. But experiments with Apollo 11, 12, and 17 Luna regolith reported challenging performance for Arabidopsis thaliana (Arabidopsis). Luna regolith seedlings demonstrated normal stems and cotyledon development. However, roots were found stunted after day 6, and the plants showed stress morphologies indicative of ionic stresses [148].

• Lettuce (Lactuca sativa L. cv. Dasusheng) was grown onboard Tiangong II Spacelab [149]. Germination rate was 37% for space and 78% for ground control. Plant morphology and number of leaves were similar but produced biomass fresh weight differed notably (space-grown lettuce was 40% lower). In nutrition, magnesium (≈ 33%), iron (≈ 35%), and calcium (≈ 45%) were lower, while potassium (by about 10%) was higher in space-grown samples. In food safety, pathogens such as Staphylococcus aureus, and Salmonella were not detected in both groups. But ground control lettuce presented a higher net colony count. Also, space lettuce grew taller, and had more deep green appearance without transitions (Figure 4).

• Parabolic flights were used to conduct microgravity research. An interesting discovery was made when thick-toed geckos were flown. Apart from a few rodents that could move by clinging to their container gratings, virtually all objects, mammals (including humans), amphibians, and reptiles float when exposed to the space environment without restraints [122]. However, when the thick-toed geckos were flown in parabolic flights, it was reported that geckos had the ability to remain attached to smooth surfaces. This peculiar capacity apparently allows the geckos to keep normal activities and behavior during weightlessness [150].

• Future studies: Planet Mars’ regolith & rocks are now being gathered by the perseverance rover. These would be studied in detail when delivered to Earth following a future sample return mission [NASA Science: Available @ Video Gallery: Perseverance Rover - NASA Mars; Accessed 12th August 2023]. I venture to speculate that the Martian regolith would be analyzed for agricultural services once in earth’s laboratories.

Figure 4.

Lettuce plant growths and appearances. In space (left), and on earth. Source: [149].

9. Dialing back the doomsday clock

The bulletin of atomic scientists and SERI study cited war, disease, climate change, and disruptive technology as the proverbial Swords of Damocles hanging over planet earth [1, 151]. Due to these threats, the doomsday clock crept 90 seconds to midnight (the ignition time and point of no return from Armageddon) on 24th January 2023. Thus, mitigation of any of the threats is tantamount to dialing back the doomsday clock.

9.1 Contributions of circular bioeconomy to climate change mitigation

Fossil fuels and inorganic fertilizers are sources of GHGs and aerosols implicated as agents of climate change. Their substitutions with benign alternatives are needed. Below, are some of the advantages, attributes, benefits, and quantified contributions of the circular bioeconomy paradigm to climate change mitigation.

9.1.1 Production of renewable energy

Biomasses are renewable energy creation inputs, and AD is used for biofuel (biogas, biohydrogen, biomethane, etc.) production [152, 153, 154]. Work with watermelon waste for bioethanol and biomethane production reported biogas yield at 581 ± 11 mLN/gVS [155]. Biogas may be used as is or converted to higher-quality biomethane [156, 157]. One study subjected cassava peeling residue (CPR) derived from 1000 kg of cassava root to AD. Output biogas provided sufficient energy to process the 1000 kg root into flour, gari, and starch [158]. Biogas canceled the global warming potential of fossil energy otherwise required for the production of these products, hence contributing to climate change mitigation.

9.1.2 Production of biofertilizer

As noted in Section 6.3, fertilizer via ammonia synthesis is a huge fossil energy consumer and GHG emitter. One ton of oil, 108 tons of water, and 7 tons of CO₂ are linked to one ton of synthetic fertilizer [159]. Inorganic fertilizer volatilizes ammonia, a known precursor [70], that enables nitrate and sulfate aerosols. Studies indicate that nitrates will be a major anthropogenic climate forcer in the future because of inorganic fertilizers in agriculture [160, 161]. Substitution with digestate biofertilizer generated from AD operations indicated viability. In cassava root production, a liquid fraction of CPR digestate could supplant up to 28% nitrogen, 11% phosphorus, and 38% potassium sourced from chemical fertilizers for cassava root production [83]. Digestate biofertilizer, therefore, seems to be a climate change mitigator.

9.1.3 Minimization of CO₂ footprint

Circular bioeconomy could decarbonize energy systems and reduce CO₂ footprint. Substituting Haber-Bosch fertilizer with digestate for example avoids the 7 tons of CO₂ emitted for each ton of fertilizer produced. Studies replaced fossil fuel with biogas in the transport sector. Biogas caused only 21–36% of the GHG emissions of fossil-based fuels [162], and biomethane reduced CO₂ footprint by 49–84% [163]. Emissions linked to AD production of renewable energy and biofertilizer were lower than those for production of fossil energy and mineral fertilizer [164]. A study of combined heat and power (CHP) production found that pressurized AD systems achieved a direct CO₂ footprint of about 13 kgCO₂/MW h_f. This footprint is quite low when compared to the 700 kgCO₂/MW h_el direct CO₂ footprint of conventional CHP systems [165]. In the analysis of sorghum cultivation as an energy crop, inorganic fertilizer accounted for 51% of GHG emissions; digestate decreased carbon footprint by 11%. Digestate was then recommended for sustainable energy crop production and GHG mitigation [166]. Furthermore, a study from Switzerland quantified their national biomass availability and confirmed its potential for biofertilizer provision and climate change mitigation. The authors concluded that by 2050, circular bioeconomy application of AD would save significant amounts of mineral fertilizer (over 10 kt/a), and GHG emissions (38 kt/a of CO₂eq) [167].

9.1.4 Ozone (O₃) and waste management

Some controls bear more benefits: mitigate climate change, and upgrade agriculture and health. Ozone control with methane reduction embodies such impacts [52, 168]. Tropospheric ozone is a GHG and air pollutant. Ozone degrades crop output and human health [71, 169]. Because methane is an ozone precursor {via oxidation reaction: CH₄ + 4O₂ → CO + H₂ + H₂O + 2O₃ [170]}, CH₄ reduction would minimize ozone and ozone’s allied ill outcomes. About 17% reduction of global methane emission per year is estimated to reduce ozone by ≈ 1 ppb, and radiative forcing by ≈ 0.12 W/m² [168]. Avoided global warming of such measures in 2050 is ≈ 0.28 ± 0.10°C [52]. Methane does arise from animal manure, municipal wastes, and landfills. Circular bioeconomy using AD as waste manager converts organic matter (energy crops/double-cropped biomasses, farm residues, animal manure, food processing wastes, space mission wastes, wastewater treatment plant effluent, organic fraction of municipal solid waste, and virtually any organic waste: whether previously sent to landfills or not), into valuable energy carriers (e.g., biogas and digestate). AD code would eliminate these ozone precursor sources, and their effects as environment-polluting wastes. As methane itself is a GHG of a global spatial scale, its reduction reduces its GHG effect; and combined with ozone & waste management, the benefits scale the entire world -all: human health, agriculture, ecosystems, countries, etc.

9.1.5 Monetization, cost savings, and energy justice

Circular bioeconomy could contribute to climate change mitigation by appealing to the morality, justice inkling, pocketbooks, and bottom lines of stakeholders. Profit margins and pecuniary savings might incentivize entrepreneurs/businesses to adopt circular bioeconomic tools. Studies monetized the benefits of climate mitigation via gains associated with O₃ management [52, 168, 171]; and cost savings inherent in the application of digestate biofertilizer [102]. Monetized benefits of O₃ reduction through NOx mitigation were estimated at $1875 per metric ton of NO₂, and that for NMVOCs at $1100 per metric ton NMVOC [171]. For agriculture, forestry, and non-mortality human health, the estimate of global annual monetized benefits of O₃ mitigation through 59 M ton CH₄ reduction included $7.8 billion avoided damages, and $1.7 billion net cost savings at marginal cost of < $81 per ton CH₄ [168]. When human health mortality, crops, and climate were evaluated, monetized benefits of CH₄ reduction as an ozone control measure were estimated at $700 to $5000/ metric ton CH₄. This value was much higher than the usual marginal costs (< $250/ metric ton CH₄) required to implement abatement solutions [52]. Likewise, a study analyzed the economic implications of supplanting the inorganic fertilizer required for cassava root production with liquid fraction digestate. Results showed that about 25% of cost incurred in chemical fertilizer purchase could be saved with liquid fraction digestate. The monetized benefits were valued at $0.141 billion for the year 2019 global cassava root output. However, this valuation was conservative as the monetization did not include external costs of inorganic fertilizers such as air pollution, eutrophication, GHGs, and the contamination of potable water supply reserves [102]. Related to profit motive is the ethical and philosophical inclinations of humans to do good albeit for self-preservation. Perhaps the moral allures of global energy access and security would prod policymakers to address issues of equity and justice in energy availability, accessibility, distribution, and affordability. Anaerobic digestion and biogas energy have been recognized to have the potential to achieve more sustainability and energy justice in society [100, 172].

10. Conclusions and perspectives

There is a palpable sense climate change is likely due to GHGs and aerosols. There is debate though, as to who or what is more blamable for their emissions. This controversy was illustrated with attributions to the hot summer of 2010 in Russia. A group of authors attributed the cause to natural events [29], while another attributed it to human actions [30]. Yet a third group argued that both sides may be correct, subject to how the data is checked [31]. So, what should citizens/ people/ the public believe? There are reports that nature continues to contribute climate change agents [22, 23, 24, 25, 173, 174, 175], and human activities are also doing the same [9, 26, 27, 28, 176, 177, 178, 179, 180]. Since at present, there is no human ability to bar natural contributors of these agents (e.g., stellar outbursts, volcanic detonations), it becomes obligatory that the human-made agents must be restricted, especially in the current Anthropocene era. This author suggests human talents and ingenuity be expended on constraining anthropogenic sources and creating mitigating alternatives.

Remarkably, climate change is no respecter of borders, be it local, national, regional, or international; and not on land, at sea, in air, or in space. Climate change does not respect wars and nations at war. Heatwave of 2010 affected countries in Europe. Helsinki in Finland recorded a daily mean temperature of 26.1°C; Kiev in Ukraine, 25°C at night, and Moscow in Russia reached a daytime temperature of 38.2°C [181]. Climate change is killing humanity; humanity should stop killing humanity. From Ukraine to Sudan, all wars on planet earth must stop. Countries should cooperate to fight common enemies of humanity (including climate change, hunger, disease, inadequate- health facilities, potable water and electricity supply, etc.); not fight each other. The industrially advanced nations that contributed most of the emissions breaching planetary boundaries, also have the resources and ability to adapt and manage the fallouts. The onus is on the technological economies to use the usual 20/20 hindsight to share answers and assist, encourage, and guide developing countries. Doing so would enable developing nations to avert the mistakes advanced countries made in their developmental trajectories.

This chapter identified ways circular bioeconomy minimize exceedances of planetary boundaries, mitigate climate change, and dial back the doomsday clock. Approaches of IRA and AD were discussed. AD is a wise way to recycle resources of land, nutrients (e.g., N, P, K), carbon, water, and sunlight [83, 101, 102, 108, 109, 115, 153, 158, 167, 182, 183]. AD converts organic matter into valuable energy carriers (e.g., biogas, biomethane, electricity, and biofertilizer) for beneficial domestic and industrial applications. In particular, the solutions of renewable bioenergy and biofertilizer provision, attenuation of carbon dioxide footprint, ozone and waste management, as well as monetization, cost savings, and energy justice were presented. These solutions are anchored to IRA in general, but more specifically to AD; a mature, cost-effective, and environment-friendly technology. Both approaches, however, could be scaled to the industrial competence of virtually any country on earth. To strengthen the robustness and sustainability of these approaches/ solutions, three additional answers are pinpointed:

1. No till crop management. This method was applied to maize (Zea mays, L.) farming and offered better economic, environmental, and ecosystem benefits as compared to other practices tested [184]. No till was also found to be advantageous in phosphorus accumulation, availability, and overall soil ecosystem function [185].

2. Reduction of food waste. Near 1.3 to 1.8 billion metric tons of food ≈ 30% of global food output is wasted annually [186, 187]. Because 24 to 30% of GHGs emanate from agriculture [59, 187], up to 10% of GHGs may be attributable to wasted food, besides emissions inherent in food decaying in trash cans, landfills, and dumpsites. Consequently, reduction of food waste would contribute to climate change mitigation.

3. Reduction of local pollution. Nations may attend to local pollutants like those generated by the transport sector. This is because local pollutants respond to the environmental Kuznets curve (EKC); Figure 5.

EKC hypothesis applies an inverted U-shaped relationship to pollution and economic prosperity. Income increases with pollution until a peak regarded as the turning point is reached. As Figure 5 shows, after the peak threshold, further rise in income results in decrease in pollution indicators [188, 189, 190, 191].

Figure 5.

A generalized schematic of the environmental Kuznets curve (EKC) hypothesis.

The chapter also highlighted the implications of circular bioeconomy for the space food system. Along with AD and IRA; CELSS, BLSS, NNC, circularity, and molecular pharming were identified as strong links to sustainable space enterprise food system. Despite the challenges of microgravity, decades of research efforts have demonstrated the possibility and capability of growing plants in microgravity environments.

Food is an indispensable requirement for life on earth and in space. Its provision in terms of production, processing, consumption, and disposal must be carefully managed to minimize the footprints of resources consumption and external costs of GHGs and aerosols on the one hand. On the other hand, the provisioning should maximize solutions that mitigate climate change. AD in the context of circular bioeconomy appears to embody viable climate mitigation solutions. Recycling with AD judiciously utilizes biomass resources to generate climate mitigation solutions (e.g., bioenergy, biofertilizer); and simultaneously reducing the waste management menace. Evidently, mitigating climate change with a circular bioeconomy would enable dialing back the doomsday clock for the betterment of humanity. Studies that engage in quantitative determination of the contributions of these solutions (including their scientific foundations, environmental strengths, and financial viabilities) would be endeavors deployed in the appropriate path.