Introduction:
The latest Climate Action Tracker (CAT November 2020) lists only two countries to be on target to limit global temperature increase to 1.5⁰C from the pre-industrial level by 2100, namely Morocco and The Gambia. The world as a whole is proceeding towards an increase of between 2.8⁰C and 3.2⁰C, twice the internationally agreed target figure. This is likely to have a dramatic effect on the environment, especially for Homo sapiens. It is conjectured that the UNFCCC Conference of Parties 26 (COP 26), originally to be held in Glasgow, UK in 2020 (and postponed due to Coronavirus until late 2021) will be a defining moment in establishing whether countries and world bodies can agree to and achieve the 1.5⁰C target. At present this seems doubtful. It will be the young and future generations who will suffer the consequences of slow actions taken by the present (senior) generations, who amble towards ‘doomsday’. It is past time for evolution. What is needed is a green revolution.

Most of the ‘energy’ goals to achieve a 1.5⁰C target increase are well known, namely reducing fossil fuel consumption, reversing deforestation, improving efficiency at all levels, promoting carbon capture and storage (CCS) and dramatically expanding the use of renewable energy. However, the underlying cause for the present hiatus in committing to the 2100 target is little mentioned, either by countries or world bodies, and that is population increase. By 2100, the estimated population of the world will be 10.875 billion (of which 88% will be in Less Developed Countries - LDCs) as compared to the 2020 estimate of 7.795 billion (83% in LDC) – an increase of 3.080 billion (Population Pyramid March 2020). 2.7 billion of this increase will be in developing countries. At the very minimum, the additional population will require food, much of which will be provided by the subsistence sector from the clearing of forests and woodland for arable and pastoral agriculture. At the same time, a general increase in wealth will promote the expanded use of fossil fuels. Not only will the increased population and rising average wealth cause further clearance of forests, woodlands and grasslands, but it will also bring about significant social challenges such as mass unemployment and the movement of people to cities and to developed countries. How are these problems to be tackled?

Tempering Population Increase:

Because of the Coronavirus pandemic, it is likely that there will be a worldwide spike in births from December 2020 and the health systems of many countries will be put under additional strain. However, measures could be put in place to temper global population increase. Restrictions on family planning services must be lifted so that all women (and men) have access to birth control measures, including abortions. The US government has banned organizations such as Planned Parenthood referring women for abortions under the ‘Title X’ rule [1] This has led to Planned Parenthood, withdrawing from this program, affecting women both in the USA and worldwide (Population Connection Vol 51, 4 Dec. 2019). On 28^th January 2021, the new Biden-Harris administration passed a presidential memorandum seeking to review this Title X rule. It is hoped that much will be overturned. This same issue points to the fact that education, especially for girls, is one of the best ways to temper population increase. Indeed, in some countries, the UN World Food Program offers cooking oil to families that send their girls to school, as I have personally witnessed in Pakistan.

The greatest population increase will be in Sub-Saharan Africa (SSA), where a rise from 1.1 billion to 3.8 billion is expected between 2020 and 2100 (Openshaw 2019). Few countries in SSA, except perhaps Botswana, have adequate family planning measures to temper this population increase. Indeed, the late President of Tanzania urged women to have more children! (Reuters 2019). Yet Africa, especially SSA, is the continent at greatest risk from the effects of global warming. Efforts must be redoubled to increase (women’s) education and to make family planning provision freely available in all countries, especially to the poor.

If the population peak could be limited to 9 billion by 2100 and thereafter start to fall, this would benefit the environment considerably. If it is assumed that the universal per capita daily food requirement is 2,000 kcal (8.4 MJ) - equivalent to 0.54 kg of grain - (U.K. National Health Service 2020) and that the average per-hectare (ha) yield for (subsistence) agriculture is 2,000 kg/year [2], then a family of five would require about 1 ha to meet their basic food requirements. If the 2100 peak population was limited to 9 billion rather than the currently projected 10.875 billion, there would be 1.875 billion fewer people by that date, of which an estimated 1.695 billion would be from LDCs. This would save an estimated 167 million ha of forests being cleared for subsistence agriculture, equivalent to approximately 17 billion tonnes (t) of carbon [3] (62 GtCO₂) stored in the wood and the soils. This is why it is critical to tackle population increase. If it is ‘business as usual’, from 2020 to 2100, the world’s population will increase by over 3 billion (including 2.7 billion in LDCs) and this could lead to a reduction of 266 million ha of forests, resulting in 27 GtC of carbon (99 GtCO₂) being vented to the atmosphere [4,5]. This does not take into account forests being cleared in the cash economy for agriculture. Replacing this through tree planting would cost an estimated 105 billion US dollars ($) in planting and maintenance costs over 35 years or $3 billion per year. (Openshaw 2015). Such funds could be invested in family planning and infrastructure development, to the benefit of future generations and the environment.⁶

Economic Development:

Developed countries have jointly guaranteed $trillions (10¹²) to assist their economies and populations to counter the effects of the coronavirus pandemic. Such sums of money could more than solve the global warming crisis, but it is doubtful if nations attending COP 26 will agree to sufficiently increase their Nationally Determined Contributions (NDCs) under the Paris Agreement (UNFCCC 2016). To approach the sums needed to meet the target figure to reduce greenhouse gas (GHG) emissions, even though the USA now intends to re-join this agreement, it will need an international perspective, rather than a national one. This reminds me of a Spaniard and a Gaelic speaker from Scotland comparing words in their language. The Spaniard talked about mañana meaning maybe tomorrow. The Gaelic speaker said “Oh we haven’t a word for that sense of urgency”! COP 26 may turn out to be just the same. This is why people, especially the young, need to act now to change governments’ minds.

Turning to economic development, there has to be a redistribution of wealth, both within and between countries, to help solve the problem of global warming. Many poor countries do not have the infrastructure or the means to greatly increase the wealth of their poorest (rural) communities. Without such an increase, however, these communities will languish in subsistence agriculture and be unable to afford electricity and other means of improving their wellbeing.

Clearly, the developing world will need to expand its (useful) energy consumption, particularly renewable energy, if it is to escape from poverty and under-development. Just as important, the developed world must reduce its energy inputs from fossil fuels through a combination of measures including improved efficiency in conversion, intermediate and end-use, energy conservation, greater use of public transport and less urban sprawl, and by switching to renewable or other forms of “low polluting” energy. It is ill-advised - both environmentally and economically - for LDCs to follow the past energy strategies of the ‘West’.

The wealthier a population becomes; the fewer babies’ women have. [6] This is true especially for the poor in developed countries, especially in China and to a lesser extent in India and other parts of S. and S.E. Asia. Natural resources are limited; supplying the necessary resources to 10.9 billion people by 2100 is likely to exceed the world’s sustainable capacity and damage the environment beyond repair for human habitation. It is up to the ‘rich nations’ and the wealthy in LDC to recognize this. Much as a pandemic affects us all, the clearing of tropical forests in Africa, Asia and South America for short-term financial gain affects all living things, especially Homo sapiens. The long-term economic costs, including environmental costs, of these actions must be taken into account. Payment to countries with large areas of tropical forests under threat, say through the ‘green carbon fund’ may not only be necessary but will be essential in order to meet the goals of the Paris Agreement.

The traded price of carbon per tCO_2e (equivalent) can vary significantly. An FAO paper # 177 (FAO 2016) gives a range from $1 to $130 per tCO_2e, with about 85% priced at less than $10 tCO_2e, ($37 tC). The paper further states that the global mitigation potential for afforestation etc. can be achieved at less than $20 per tCO_2e ($73 tC). According to the Carbon Emission Futures (2020), the March 2020 carbon credit price is between $16 and $17 per tCO_2e ($59 to $62 tC), but this covers a range of carbon pricing.

In 2018, the estimated loss of forest in Brazil, DR Congo and Indonesia was 1,349,000 ha, 481,000 ha and 340,000 ha, respectively, for a total of 2,170,000, (Quartz Africa, 2020). If it is assumed that, on average, the forest stores 100 tC [7] per ha in the trees and soil, then at a price of $59 tC, the loss is worth about $12.8 billion. For all tropical forests that were cleared in 2018, the value of the cleared areas could be worth $15 to $20 billion in carbon credits alone! This indicates not only their economic value, but also the environmental importance of preserving tropical forests worldwide and managing them properly, by paying government and especially forest dwellers to preserve them. REDD+ (Reducing Emissions from Deforestation and Forest Degradation) allows for payment of a carbon credit through the Clean Development Mechanism (CDM). The price per t of carbon has ranged from $27 to $69 (Schneck et al 2011). A price of $147/tC is deemed necessary for the CDM to be successful (Carr and Hestor 2018).

Improving Agricultural Productivity:

Nitrogen, phosphorus and potassium (NPK) are essential minerals for plant growth. These are normally supplied to commercial agriculture from mining operations or from industrial production using fossil fuels.[8] Because of cost and distribution difficulties, many subsistence farmers cannot obtain these inputs or obtain them in adequate quantities. There are alternative solutions to obtain sufficient quantities of NPK. Traditionally spreading farm-yard manure was a common practice as well as crop rotations with clover etc. – nitrogen fixing species. Many leguminous plants fix nitrogen through a symbiotic relationship with bacteria that live in their root nodules. Some farmers intercrop with these legumes such as a maize and beans or plant a cover crop of clover. No-till farming also retains some nutrients from the previous years’ crops. There are several nitrogen-fixing tree species which can further improve yields. Planting rows of these trees in fields or pasture can not only supply nitrogen, but at the same time generates stick wood for energy and other purposes. These systems have been termed agro-forestry and their promotion is led by the World Agroforestry Centre (ICRAF), part of the Consultative Group for International Agricultural Research (CGIAR). There are many agro-forestry programs. I was program director for a 5-year USAID-funded Farm Tree Planting Project in Rwanda in the 1970s. Tree planting was revived after the genocide and Rwanda has an overall 2 million ha tree planting program, including farm trees (Nash 2020) and may now meet its UNFCCC NDC target. In addition, Rwanda is extracting methane from Lake Kivu for power generation and for direct use by consumers (Zarembka 2019).

The US National Academy of Science published a book entitled Tropical Legumes: Resources for the Future (NAS 1979). This should be part of the libraries in all tropical agricultural departments and research centres; extension workers should read and use it. There are many existing nitrogen fixing trees (e.g. Acacia sp.) on such lands and increasing their presence must be encouraged. Trees are a nutrient pump, transferring minerals from lower soil horizons to the surface via leaves. Trees also attract beneficial birds etc. which keep down harmful insects. Nitrogen-fixing tree species can be used to intercrop in place of shifting cultivation and to eliminate the invasive grass species Imperata cylindrica, (ICRAF 1999). Brassicas (cabbage etc.) and beans planted side by side can deter the black bean aphid (Aphis fabae) from attacking the cabbage. Another intervention was applied to maize in East Africa. Scientists from Rothamstead agricultural research facility (U.K.) found that planting napier grass (Pennisetum purpureum) round the edges of maize fields and intercropping the maize with molasses grass (Melinis minutiflora), deters stem borer moths (Busseola fusca and Cholo partellus). These grasses also attract parasitic wasps that prey on the stem borer moths. Not only do yields of maize (and sorghum) increase, but the two grasses are also edible fodder for cattle, which meant that farmers can increase their animal stock and provide more milk and dung to fertilize the fields (The Guardian Weekly 2003). The grasses also increase the amount of carbon stored in their roots and the soil. Again, one of the curses of farmers on poor land in Africa (and elsewhere) is witchweed (Striga asiatica) (CABI 2011), which parasitizes the roots of cereal crops and kills them. The striga seeds can lay dormant for many years and are difficult to control. The same scientists found that a tree legume (Desmodium uncinatum or silverleaf), if intercropped with maize, resulted in no striga invasion, while adjacent maize fields without silverleaf were nearly devastated by it. This more than doubled the yield of maize and the silverleaf provides cattle fodder and stick wood, (The Guardian Weekly 2003). These are but some examples of the beneficial symbiotic relationship between plants that can be adapted by farmers, especially in the subsistence sector, to increase plant and animal yields. Another useful (C4) tropical plant is vetiver grass[9] (Chrysopogon zizaniodes). This is a bunch grass which is used against soil and wind erosion, is an excellent animal feed and stores carbon in its roots and stems.

Nitrogen-fixing tree species such as Prosopis spp., including mesquite, can be used to reclaim dry areas, but the total carbon accumulation may only be in the range of 3 to 5 tC/ha/yr. Mesquite is sometimes regarded as a weed species because animals, especially ruminants, eat the leaves and the seed pods. However, they cannot digest the seed, which is passed out with the dung. This generally regenerates and spreads. But, if the seed pods are collected and milled, thus destroying the seed, the resulting product can be sold as an excellent animal feed. All legumes, especially tropical tree legumes, have a critical role to play in land reclamation and improving agricultural productivity.

Phosphorus (P) is an essential element for plant growth, but on acid soils, P (plus N & K) may be unavailable because it is locked up. Applying lime (calcium hydroxide – Ca[OH]₂), to the soil to increase the soils alkalinity (pH>6) could release P (N & K) to the plants. There is an urgent need for soil testing to be provided to all farmers, especially subsistence farmers, and advice given as to the amount of lime, if any, to be applied to the fields. This should be part of governments’ agricultural extension services. If necessary, (subsidized) lime could be provided to farmers. Local lime producers could benefit from such an initiative, as would the farmer and the environment. Pasture land could be planted with nitrogen-fixing tree species covering about 10% of the area to provide improved fodder and shelter for animals. P is present in urine and dung so pastures could benefit from increased animal numbers. The slurry from biogas digester provides a superior natural fertilizer for farmers etc. This will be discussed later.

Potassium (K) is the third essential element for plant growth. As mentioned above, increasing the hydrogen ion concentration (pH) of the soil would make more K available to the plants. Another ready source of K is wood ash (potash). Wood ash is relatively rich in K, in the form of K₂O (1% to 10%), as well as in lime. Many subsistence families still cook on wood-fired stoves and so the potash could be collected and applied to the fields or at least the ‘home garden’. There is also an opportunity for wood-fired power systems (or power and heat systems) to sell the wood ash as a fertilizer. Mulching of plant residues and applying the mulch to the land will also improve soil fertility.

There are other elements that can help with plant growth. Carbon is one. Black carbon has been criticized because, if it lands on snow, it absorbs the sun’s energy, rather than being reflected back. However, the benefits of adding carbon to the soil far outweigh the costs, especially in the tropics. Carbon added to the soil in the form of soot improves the soil-water quality. It is a valuable fertilizer. (Sootbosters: www.suitebusters.org). It is changed by bacteria into nitrates, in which form it is available as a plant food. (Oakbrook Chimney Services 2018). Copper is a trace element that is deficient in some soils. Soil testing could provide information about this and other trace elements and allow appropriate treatment regimes to be recommended. Trees build up the soil carbon content through surface litter decomposition and the death of roots, rootlets and bacterial activity in the soil. The minimum annual increase per ha in short-rotation tree growth is 0.82 tC/yr. (Silver et al 2000). The greatest store of organic carbon in soils is in tropical high forests. (Pan et al 2013), followed by woodlands then grasslands. Arable agricultural areas have the least store of soil carbon per ha. This carbon store could and should be increased by improved farm management and silvicultural practices.

Many watersheds are being converted to agricultural areas or trees are being over-cut. This is subjecting such areas to flash floods, causing mud slides and the destruction of property and agricultural land. It also seasonally diminishes the flow of water, thus affecting the livelihoods of the surrounding population. The REDD+ program could and should be used to save such areas: they should be given priority. In India and Pakistan, groundwater from aquifers is being overused for the production of agricultural crops. This cannot continue and more economical irrigation methods have to be used if the groundwater is to last. Otherwise, food production may have to rely on rainfall, with a fall in yields and the inevitable abandonment of some agricultural land!  On a practical note, more water could be stored by households and schools, especially in Africa. When it rains, much of the water is not collected but flows away. In Thailand, for example, rainwater from the roof is collected in ceramic tubs and used for a multitude of purposes. This practice could be copied by households world-wide. I was asked about setting up a market garden and tree nursey in a rural African school, which had to rely on rainwater. I suggested that the rainwater from the school roof could be collected in a simple lined sand-trap and used to water the allotment when required. I also stressed that students should be taught about environmental protection and improved farming methods, such as alternatives to shifting cultivation.

Shifting cultivation is a method whereby farmers can grow crops for two or three years on cleared forest areas, before the crop yields become too low for sustenance. The farmer then moves to a new forest area and repeats the process, allowing the former cleared lands to recover for about 20 years before the cycle is repeated. Due to increased population pressures, however, the recovery cycle in many cases is shortened and the cropping time is curtailed, resulting in lower yields and shorter recovery times. Inter-planting such areas with nitrogen-fixing crops, especially tree species, can stabilize agricultural productivity and provide animal browse and/or mulch to the soil, as well as stick wood, eliminating the need for the farmer to move on. Planting shelterbelts and hedges reduces evapo-transpiration of agricultural crops to increase yields. These are used in several countries from China to Egypt and have world-wide application where seasonal winds are normal. The best practices from countries throughout the world should be publicized and promoted. Also, silvicultural productivity has to be increased.

Renewable Energy, especially Biomass Energy:

According to the International Energy Agency (IEA 2018), out of total global energy demand of 598.8 EJ per annum, biomass and waste accounts for 59.5 EJ (10%). Hydro-electricity accounts for 15.2 EJ (3%) and other renewables for 12.1 EJ (2%), bringing the total for renewables to 86.8 EJ (14.5% of total demand). Despite its great significance, biomass - especially woody biomass used by poor people in developing countries - is neglected by energy planners and governments, except as a fuel to transition away from, for it is regarded as polluting and unsustainable as currently used by households in its present forms of fuelwood and charcoal. Out of a mid-2020 estimated global population of 7.76 billion, 6.5 billion are in LDCs, of which at least 4 billion will be using traditional (woody) biomass for cooking (and heating). This figure is likely to increase by 2100 as the population in LDCs may reach nearly 10 billion, unless steps are taken to actively temper population growth (Openshaw 2019).

The World Bank has stressed the importance of assisting the private sector, e.g. World Bank Development Reports: www,worldbank.org; biomass energy production is principally in the hands of the private informal sector and is a fuel consumed by the poor (and rural industries). Yet very little help is afforded to such people. From personal experience and 40 years residency and working in developing countries, development banks could assist through training, market intelligence, encouraging the removal of inappropriate bans and restrictions and improving infrastructure. Above all they should ensure a level playing field regarding fuel subsidies.

At present, most fuelwood is burnt inefficiently on three-stone fires and this generates products of incomplete combustion (PIC), which are deleterious to health and cause premature deaths, especially so if the stove is indoors. Relatively low-cost improved stoves have been promoted for some time. Barnes et al (2012) concluded that improved stoves should be based on what the cook wants, rather than maximum efficiency. Critical parts should be manufactured commercially (as in China) and the price should be affordable, with little or no subsidies. If stoves are bought rather than given, they will be used all the time. There are also simple things that can be done such as ensuring adequate ventilation, adding a chimney to the stove, using dry wood, pre-soaking hard foods (e.g. beans) and keep children from the kitchen. If there is a chimney, the soot can be collected periodically and used as a fertilizer. There are more efficient wood-gas stoves on the market, but these cost in the region of $30+ and are beyond the reach of the subsistence farmer and the urban poor. As economic opportunities improve, such stoves may become affordable.

Charcoal is a relatively smokeless fuel with very few PICs, except at the lighting stage, when carbon monoxide is produced. Cooks know this and therefore light their stove outside before it is brought into the kitchen. Charcoal can be bought in small quantities, hence its use in urban areas, especially in LDCs. The charcoal production process is wasteful in the sense that up to 60% of the original energy is lost in the conversion process, but the resulting fuel has twice the energy per unit weight of the parent material, is less polluting and is more convenient to use. This wastefulness is decried by some, but the same argument is hardly ever applied to electrical generation from fossil fuel, when up to 75% of the energy may be lost in production and distribution. Of course, charcoal production can be improved, and producers should receive training in woodland management, charcoal production and in marketing. Charcoal production should be treated as a legitimate activity that is supplying a renewable and convenient energy form, while generating rural employment in production, transport and trading. There are petroleum engineers and electrical engineers, but there are few biomass engineers (charcoal, methanol/ethanol, biodiesel, biogas/producer gas). Yet these are, or could be, important fuels and their status would be enhanced through systematic university or technical training in their production and use.

Regarding improved stoves, in 1979, I compared the traditional metal stove (jiko) used in East Africa with the ceramic bucket stove from Thailand. (Openshaw 1979). It was found that the bucket stove was about twice as efficient as the jiko. When I moved to Kenya, to work on a Beijer Institute (now the Stockholm Environment Institute) fuelwood cycle project, I organized a stove testing competition for KENGO (Kenya Energy and Environment NGO) at the UN New and Renewable Conference in 1981. This aroused much interest and USAID financed an Improved Stove Program (ISP) within the Ministry of Energy. At the same time, I was involved in an Improved Stove working group. Through the Beijer Institute, I arranged a trip to Thailand for the ISP project manager (PM) and a potter from Clayworks Ltd. in Nairobi to examine charcoal stove manufacture. The PM returned full of enthusiasm for the Thai stoves. A private firm (Jerri International) worked with the PM and together they designed a clay-lined stove. This stove was field tested with women’s group and modified accordingly. In 1983, I was appointed the regional director of a USAID funded project entitled Energy Initiatives for Africa. Through that project, USAID financed a ‘Regional Stove Training Program’ with KENGO. This program trained stove makers throughout Eastern and Southern Africa in all aspects of the stove business. The resulting clay-lined jiko was commercially manufactured and became very popular. Through the Stove Training Program, many people throughout Africa received training and improved clay-lined stoves are now manufactured across the continent. While such stoves are commercially manufactured, there is a role for government to ensure quality, run training courses and demonstration and - if required - provide loans. This was a very successful South-South initiative. I was proud of the part I played in introducing more efficient charcoal stoves to Africa.

Biogas from crop and animal waste is important in some counties, such as China and India. It contains about 60% methane and has an energy value of 30.5 MJ/kg (22.6 MJ/m³). The slurry provides an excellent fertilizer and importantly it kills most if not all pathogens in the feedstock. One drawback to biogas production is the cost of the digester and appliances, which is $500-600 per unit. The individual farmer also requires the equivalent of four healthy cows. There are cheaper and smaller digesters that cost about $100 and can be used by individuals using household and pig waste and vegetation etc. (IRENA 2017). These have both health and fertilizer benefits: it may pay from an environmental viewpint to subsidize such units.

There are two types of bacteria than anaerobically break down plant and animal waste, namely mesophilic (operating at 30^-40⁰C) and thermophilic (operating at 50^-60⁰C). The former is used in tropical countries, while the latter can be used in temperate countries if some of the biogas is used to heat the substrate. Sewage plants etc. throughout the world could use thermophilic bacteria to produce biogas as a part substitute for natural gas (methane) from fossil fuels, especially if a carbon tax is placed on such fuels! One important fact is that coronavirus and similar viruses are present in animal faces. Sewage works and factory farms should install appropriate digesters to kill such viruses. The biogas could be a substitute for fossil-fuel methane, especially if a carbon tax is placed on such a fuel and the slurry substituted for artificial fertilizers - a win-win situation.

While household biomass is the dominant energy use, especially in LDCs, it is also used by many people in industrialised countries, especially for domestic heating. From various demand surveys undertaken by the Energy Sector Management Program of the World Bank, non-household use accounts for about 10% of biomass energy consumption in LDCs. It is used for crop drying and food processing, in the ceramics industries, for brick burning, lime production and in the service sector - restaurants, food shops, school canteens etc.

Biomass is also a feedstock for heat and power production worldwide (0.5% of the total), although electricity generation from water, wind and the sun dominate the renewable energy mix and account for 23% of total electricity production, equivalent to 96 EJ in 2018 (IEA 2018). Electricity production accounts for 16% of energy demand.

Motor ethanol and biodiesel are produced from sugar, maize and plant oils. In the US, all gasoline (petrol) contains 10% ethanol. The US and Brazil are the largest producers of ethanol, whereas such countries as Indonesia and Malaysia lead the production of biodiesel. Production of these fuels is expanding, although in the US maize (corn) production is subsidized. Biodiesel from plants such as Jatropha curcas is expanding; this tree can be grown on marginal land, although it needs nitrogen fertilizer to maintain its productivity. Inter-cropping with nitrogen-fixing (tree) species may solve this problem. In 2018, the estimated demand for liquid biofuels was 419 PJ or 3.5% of motor fuel demand (IEA 2018).

Hydrogen has been proposed  as the new and renewable energy of the future, especially in developed countries (Hydrogen fuel: www,hydrogenfuel.org). Hydrogens 4.3 times the energy value of carbon per unit weight (141.7 MJ/kg compared to 32.8 MJ/kg for carbon), but its impact in LDCs will be negligible, especially in rural areas. Also, because all fossil fuels came from biomass, biomass can be and is turned into solid, liquid and gaseous fossil fuel substitutes. It may be cheaper and safer to use renewable carbon-based fuels than to rely on hydrogen. Indeed, because hydrogen is difficult to handle, it has been suggested  ---- that methanol (CH₃OH) be the ‘carrier’ for hydrogen. Methanol can be produced from the dry distillation of biomass (wood alcohol), therefore, why not use methanol directly rather than as a hydrogen carrier?[10]

The amount of carbon dioxide (CO₂) in the atmosphere today is estimated to be 410 parts per million (ppm) and increasing at over 2% per year. The estimate in pre-industrial times was 280 ppm. One way to reduce CO₂ in the atmosphere is through carbon capture and store (CCS). Capturing CO₂ from power plants and cement factories and sequestering it belowground in leak-proof areas or in oil wells has been proposed (Bryant 2013). The cost of CCS using this method is at least $60/tCO₂. (Openshaw 2016). This only captures CO₂ from specific sites, whereas it is universally emitted. A cheaper method with global applicability is CCS in trees and soils. Between 2015 and 2050, about 1,540 GJCO₂ (420 GtC) will be released to the atmosphere (IPCC AR5 2014), of which an estimated 154 GJCO₂ (42 GtC) will be from forest clearing for arable and pastoral farming etc. To capture 42 GtC in tropical and temperate plantations (or their equivalent) would cost in the region of $121 billion (optimistic) to $188 billion (pessimistic) and require 115 to 172.5 million ha (3.6% of farm and grassland). This works out at a cost of $0.78 to $1.17 per tCO₂, excluding the cost of the land (which may add another $3.00 per tCO₂ to the cost). This capture is for storage and use. If only storage is considered then on average only 19.32 GtC out of 42.00 GtC are stored and this increases the cost to between $1.69 and $2.39 per tCO₂, [11] excluding land costs, but it is still far cheaper than sequestration below ground etc. What is more, when the plantations are mature, there will be an annual sequestration of wood and soil carbon of 15.50 tC/ha of which an estimated 10.92 tC/ha (1,256 million tC) will be in stem and branch wood, from the proposed 115 million ha (Openshaw 2015, corrected version). Such an amount of wood could be used for biomass energy, construction and/or other purposes.

Each year, plants fix about 100 billion t of atmospheric carbon through photosynthesis, of which about half – 50 GtC - is from land plants (the carbon cycle), (Hall & Rao 1994). Some of this is used for food and biomass energy etc. before it decays and returns to the atmosphere: 50 GtC has an energy value of 1,640 EJ. Annual use of biomass energy accounts for 60 EJ and food production (including animal feed) for 107 EJ (Berners-Lee et al 2018) and between 15 and 25 EJ could be added in trees, grasslands and soils.[12] This represents under 12% of annual land plant production. Much more of the annual carbon sequestration could and must be used, before it returns to the atmosphere.

Wood is the most convenient form of biomass for energy purposes. For the world as a whole, and for LDCs in particular, the annual growth of wood is 3 to 4 times annual demand, (Openshaw 2011). It is not the use of wood that is causing ‘deforestation’ but the clearing of land for arable and pastoral agriculture (and urbanization) as a result of population increase and the need to generate cash income. There are areas in LDCs where trees are being over-cut and other areas where there is a surplus. Many proposals have been made to reduce consumption and increase supply, which I and others have made while working in LDCs for various development agencies.

It is not the ‘traditional’ collection and use of biomass energy that is unsustainable, rather it is the policies of developed countries and one-sided ‘market’ solutions that are unsustainable: this is accelerating deforestation and keeping many rural communities in poverty. From personal experience, alevel playing field with regard to subsidies for agriculture (and energy) will do more for development than the current trade and aid policies.

There has been an upsurge by individuals, NGOs, government and international organizations to increase tree planting as a means to offset global warming. A publication from the Crowther Lab, part of the ETH Zurich University (Bastin et al 2019), estimates that 900 million ha of land is potentially available for tree planting. Tree cover on this land could absorb two-thirds of the CO₂ that human activities have emitted since the start of the Industrial Revolution. According to the Climate Action Tracker of the Global Carbon Project, since 1751 the world has emitted over 1.5 trillion t of CO₂ (409+ GtC). (Ritchie & Roser 2017). A similar quantity of emissions - 1,540 GtCO₂ (420 GtC) - is anticipated between 2015 and 2050 (IPCC AR5 2014). This is why it is necessary that tree planting be an essential part of the Global Warming Initiative, coupled with tempering population increase. The cost of capturing 1.5 trillion tCO₂, could be in the region of $1.5 to $2.5 trillion, including carbon capture and storage, but this could be spread over 80 years. Other costs include family planning, rural development, infrastructure development, and payments to preserve tropical forests. This could bring the total cost of achieving the goals of the Paris Agreement to keep temperature increase to 1.5⁰C above the pre-industrial level to a ballpark estimate of $2-3 trillion. This is the minimum amount that industrial nations have pledged to fight the coronavirus pandemic. Saving the world from the effects of global warming is a necessary and vital investment to ensure Homo sapiens’ survival.

In 1966 I wrote a paper for the Fabian Society about improving the economics of remoter rural areas in the U.K. (Openshaw 1966). One recommendation was a 10 million-acre program (4.05 million ha) to plant trees by 2000.[13] It was received rather sceptically by the conservative press. Peter Simple wrote in his column in the London Daily Telegraph, “What are all the (horrid) regimented rows of conifers for”? With tongue in cheek, I replied that it is to hide all the comrades behind, come the revolution!

Now the present U.K. Conservative government proposes to substantially increase the planting of trees to capture more atmospheric carbon and to curtail erosion and decrease flash-flooding etc. Perhaps the U.K. government should have an aspirational tree planting target of 10 million ha (24.71 million acres) - 40% of the land area, similar to that of Norway! This would cost in the region of $25-30 billion, excluding the cost of land. Planting and management would be spread over say 35 years, giving a carbon capture and store of 0.74 Gt by 2055.[14]  Perhaps the U.K. government can take the lead in encouraging nations attending COP 26 in 2021 to sufficiently increase their NDCs under the Paris Agreement (UNFCCC 2016), to match the amount needed to meet the target figure to reduce GHG emissions? The ‘young-comrades’ can emerge from the trees and join Greta Thunberg to fight climate change. It is her generation and future generations that will suffer from the present inadequate measures.

Conclusions:

This paper has stressed the importance of population increase, which is accelerating global warming. Concerted efforts have to be made to temper this increase, otherwise it  is more difficult to achieve a target temperature increase of 1.5⁰C above the pre-industrial level by 2100. The temperature increase has already reached 1⁰C (Climate Action Tracker 2020). Solutions have been proposed to temper population increase and to intervene in both biomass supply and demand levels. On the supply side, proposed measures include increasing agricultural (and silvicultural) productivity, increasing tree planting significantly, including carbon capture and storage, adapting methods to improve agricultural output; including agro-forestry and paying people to preserve tropical forest and so on. With help and improved management, it can be used to improve agricultural productivity and stabilise the environment, add to the store of organic carbon and generate additional income. Expanded biomass use could be a key ingredient in the initiatives to alleviate poverty.

Additionally, trees can provide browse and fodder for animals; the manure from these animals can be used directly or indirectly as fertiliser rather than being used as unprocessed fuel (as happens in several countries such as India where wood is scarce[15]). Again, trees etc. can reclaim marginal land and improve the microclimate through shelterbelts and hedges on rainfed and irrigated arable lands and protect watersheds, thus benefiting lowland agriculture and hydro-dams etc. amongst other measures.

On the demand side, this paper has concentrated on biomass energy initiatives, because at present it as treated as a fuel of the past to be substituted by ‘clean energy’ (solar, water, wind) rather than a ‘Cinderella’ fuel that has a bright future. Biomass is the most important renewable fuel at present and should be embraced as a legitimate, renewable and versatile carbon-based fuel that is used in unprocessed and processed forms or used as a feedstock for electrical generation and motive power. After all, all animals, including humans, rely on carbon-based fuel (food)[16] for energy and there is no reason why biomass should not be a significant part of the world’s energy mix in the future, together with supply-side initiatives and population-tempering activities to help solve the global warming crisis. They are win-win solutions.