Our Renewable Future

Chapter 5. Other Uses of Fossil Fuels: The Substitution Challenge Continues

This chapter explores three broad categories of energy use. The first considers ways in which energy becomes embodied in infrastructure and manufactured products (primarily through the use of high levels of heat). The second has to do with the creation of lower-temperature heat for heating buildings and domestic hot water. The third has to do with the use of fossil fuels as feedstocks for chemicals and plastics. As we will see, the second of these three (heat for buildings) is probably the easiest to address with efficiency measures and renewable energy, while the first (high-temperature heat for industrial processes) poses possibly the highest substitution hurdle of all for 100 percent renewable energy systems.

High-Temperature Heat for Industrial Processes

The production of many common materials—including steel and cement—requires extremely high heat (fig. 5.1). For example, making cement (the key ingredient of concrete) involves feeding crushed limestone, clay, sand, and other ingredients into a cement kiln kept at 1450°C (2700°F); kilns are often as much as 20 feet in diameter and up to 750 feet long.[1] Although the cement industry is responsible for only one-quarter of one percent of total U.S. energy consumption, it is the most energy-intensive of all manufacturing industries.[2] The main fuels consumed in the process are coal and petroleum coke, though natural gas and oil are also used. It’s hard to imagine cement being made any other way, but it’s also hard to imagine living without it: concrete is essential to nearly all building construction as well as to roads, dams, aqueducts—and pads for wind turbines.

The main ingredient in the making of steel is pig iron, which is in turn produced in a blast furnace. The primary fuel for the process is coke (made from coal). Steel is essential in the construction of transport vehicles, agricultural machinery, telecommunications infrastructure, and buildings—indeed, the entire scaffolding of industrial civilization. Steel is also used to make rebar, which is used in all forms of concrete to provide tensile strength. There is no modern concrete construction without steel. Use of rebar also means that all concrete structures will inevitably succumb to corrosion.

WEB Figure 5-1 Temperatures used in industrial processes
Figure 5.1. Temperatures used in industrial processes.
Source: Euroheat & Power, Ecoheatcool Work Package 1 (Brussels: Euroheat & Power, 2006).

The industrial processes that are used to manufacture renewable energy sources (wind turbines, photovoltaic panels, flat plate collectors, and solar concentrators) need high temperatures, as do factories that make electric trains, electric cars, computers, light-emitting diodes (LEDs), and batteries or their components. The production of glass uses temperatures up to 1575°C; the recycling of aluminum needs 660°C; the recycling of steel occurs at 1520°C; the production of aluminum from mined ores needs 2000°C; the firing of ceramics occurs at 1000°C to 1400°C; and the manufacturing of silicon microchips and solar cells uses heat at 1900°C.[3] Relatively little process heat currently comes from electricity, as Figure 5.2 shows.

WEB Figure 5-2 Sankey diagram of process energy in US manufacturing sector
Figure 5.2.  Sankey diagram of process energy flow in US manufacturing sector.
Source: U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy, “Static Sankey Diagram of Process Energy in U.S. Manufacturing Sector”.

How could we obtain these high levels of heat without burning fossil fuels? There are four main options: electricity, solar thermal, burning biomass or biogas, and hydrogen. Let’s consider each in turn.

Electricity

It is of course possible to create heat from electricity. We do so at the household level with electric heaters and electric cookers, and industrially with kilns and arc furnaces, that are used for producing cast iron and recycling steel. Moreover, converting electricity to heat is efficient, in that nearly all the energy is converted.

But this way of using electricity tends to be economically inefficient. It takes 2 to 3 kWh of coal or gas thermal energy to make 1 kWh of electricity[4]; thus it is roughly two to three times cheaper to make heat by simply burning fossil fuels directly than to convert electricity to heat. This means if solar or wind power is at grid parity (i.e., if it costs about as much as power from a coal- or gas-fired plant), then using it to make heat will be two to three times more costly than burning coal or gas. As we have noted, electricity is high-quality energy, whereas heat is the lowest-quality energy: we currently use a lot of heat to make electricity. So to use electricity to make heat is a little like going to the trouble of turning gold into lead. Moreover, electrifying basic industrial processes while we are also electrifying a lot of transportation will add further to the already daunting task of producing all our electricity from renewable sources.

Solar thermal

Many concentrating solar thermal generating facilities, which use arrays of mirrors to focus sunlight on a small area, achieve very high temperatures. Parabolic trough systems only achieve temperatures of about 400°C,[5] but point concentrators (including parabolic dish systems, solar power towers, and solar furnaces) can produce temperatures up to 3500°C (6332°F), high enough to manufacture steel and cement, as well as microchips, solar cells, and carbon nanotubes. Further, this level of heat can be achieved in just seconds. The world’s most powerful solar furnace, in Odeillo, France, built in 1970, has a power output of 1 MW.

WEB Image 5-1 Odeillo solar furnace
Solar furnace in Odeillo, France. (Credit: Björn Appel, via Wikimedia commons.)

However, there are significant challenges to building industrial-scale solar thermal cement kilns and blast furnaces. It is unclear how a focal point of intense heat could be expanded to a controllable system. In a cement kiln, for example, the main calcining reaction takes place around 1000°C, whereas the major clinkering happens at 1400°C to 1500°C—all within the same 40-meter kiln. Perhaps molten salts could deliver heat of that magnitude, or perhaps cement kilns could be redesigned to have a solar focal point at the current burn zone. For iron smelting, it’s also unclear how the heat would be delivered to the furnace and maintained at the 2000°C level.

A perhaps greater challenge is the fact that these high temperature processes rarely shut down because cooling can badly damage the brickwork lining them. This raises the issue of heat storage to offset the problem of cloudy or rainy days or nighttime at our solar furnace; there would need to be very short-term storage to kick in if the sun goes behind clouds and delivered temperatures drop. But we don’t have good ways to store large volumes of high-temperature heat (low-temperature heat is fairly easily stored in the form of hot water). “Storing work”—that is, just working when the sun is out—could be an option for some high-temperature processes but probably not for metal smelting and cement making; and it would make winter workdays very short at high latitudes.[6]

The problems of heat intermittency and heat storage suggest the efficacy of “batch” production over continual production. However, this would necessarily be production at lower volume, higher cost, and lower efficiency.

Finally there is the question of scale. The largest solar furnace in the world, as noted, is 1 MW, and it is a big installation with 60 heliostats. In the United States alone, heat demand in the residential, commercial, and industrial sectors combined is about 15 exajoules.[7] With a capacity factor of 20 percent, the solar furnace at Odeillo represents 1/4,000,000th of the heat demand in the United States; even if high-temperature heat is only one-third of the total heat demand, our world-leading solar furnace still provides just about one-millionth of the high-temperature heat used industrially in the United States. Providing the rest of that heat with solar furnaces would imply a lot of furnaces, with a huge footprint.

Biomass and Biogas

Prior to the introduction of coal, charcoal was widely used for smelting metals. In many respects it is superior to coal: charcoal burns hotter and contains far fewer impurities. Further, when it comes from a sustainable source, burning charcoal is carbon-neutral.

This raises the question of why the use of charcoal in metal smelting largely died out. We’ll answer that in a moment. But first it is important to note that charcoal-based smelting still flourishes in Brazil, which has large iron deposits but little domestic coal. It is the world’s largest producer of charcoal and the ninth biggest steel producer.

About half of Brazil’s charcoal industry relies on plantations of fast-growing eucalyptus, cultivated specifically for the purpose, with the rest sourced from native forests through deforestation and from the use of sawmill by-products. While in medieval Europe charcoal-making was a cottage industry, Brazil has scaled up the process to encompass thousands of charcoal kilns operating at any one time.

But could other countries do what Brazil does? Probably not. During the nineteenth century, when charcoal was still widely used industrially in the United States and elsewhere, forests were being cut at a rate far above that of regrowth. Meanwhile, we were producing only a small fraction of the steel being made today. There is, quite simply, not enough forest in the world to enable this option to be deployed on a large scale. Just compare China’s annual steel production (over 800 million tons) with Brazil’s (34 million tons)[8] and consider the fact that Brazil’s carbon emissions from steel production have increased in recent years due to deforestation, even though the proportion of coal used declined. To supply the charcoal needed by the steel industry entirely from renewable, plantation-grown trees, an additional 1.8 million hectares of land (4.4 million acres) would need to be dedicated to charcoal production.[9] And we haven’t even considered using charcoal for production of cement and for other high-temperature processes.

Aside from charcoal, biogas could also theoretically do the job—if you could get enough of it. Methane can be harvested from landfills, or be produced in human waste, animal waste, or food waste digesters. The World Bioenergy Association estimates that biogas production could potentially grow to equal about one-third of the current global natural gas supply.[10] Remember, though, that we are also counting on biomass and biogas as electricity sources to balance the intermittency of solar and wind; and (in the case of biogas) possibly as a renewable transport fuel as well. Remember, too, that we are assuming reduced landfill waste in the renewable future and increased use of organic waste for agriculture.

Hydrogen

A recently published roadmap for 100 percent renewable energy[11] suggests the use of hydrogen for high-heat industrial processes. One discussion elsewhere in the literature with regard to cement production using hydrogen notes the following:

Due to its explosive properties, hydrogen could not be used in existing cement kilns, but could principally be utilized after dilution with other gaseous fuels or inert gases like nitrogen or steam. Furthermore, the combustion and radiation properties of hydrogen differ significantly from those of the fuels being used today in the cement industry meaning that—even if handling problems were solved—the clinker burning process would have to be significantly modified. By pre-combustion technologies, only CO2 from fuel combustion, but not from limestone decarbonation can be captured.[12]

In essence, the substitution of fossil fuels with hydrogen in cement making (and other high-heat processes) is theoretically possible but would require a massive redesign of these processes. Estimates for the cost of cement production using hydrogen are inevitably vague and seldom include the costs of process redesign (plus testing, piloting, scaling, and commercialization) that would have to occur.

Using hydrogen for a wide range of industrial processes would require a scaling up of electricity production in order to make the hydrogen, again adding to the already significant challenge of replacing existing fuels in the electricity sector. In addition, there would be costs and challenges associated with storing hydrogen (which, as mentioned earlier, takes up significant space and has a pronounced tendency to leak). Also, because it is so “leaky,” every industrial plant using it would have to build and operate its own hydrogen production plant as well, since hydrogen can’t be centrally produced and distributed by pipeline like natural gas.

Low-Temperature Heat

Space heating, water heating, and cooking require relatively low temperatures, and these activities dominate household energy consumption. In addition, many industries use low-temperature heat for processes that include drying seed crops, sterilizing food and medical equipment, boiling and distilling, and making paper and textiles. Most of the energy used to provide this heat is in the form of natural gas or electricity. Powering these activities with renewable energy poses a challenge, though much less of one than the high-heat activities discussed previously.

Low levels of heat can be supplied with electricity via electric heaters and heat pumps, by solar thermal collectors, and by geothermal sources. In addition, there is a very large potential role for the greater use of insulation and passive solar design in reducing the need for heating and cooling of buildings. Let’s look at these strategies one by one.

Electric Heat

As noted in the previous section, the conversion of electricity to heat can be accomplished very efficiently; however, this use of electricity is usually not economically competitive. Nevertheless, in an all-renewable future where our dominant energy sources provide electricity directly, it may make sense to electrify space heating and cooking while reducing the need for energy use by designing buildings and systems for greater efficiency. One device that could help electrify more space heating economically is the heat pump.

A heat pump is a device—usually powered by electricity—that moves heat in the direction opposite of spontaneous heat flow by absorbing heat from a cold space and releasing it to a warmer one. The same device can often serve as an air conditioner and water heater. There are two main types of heat pumps used in buildings: ground-source and air-source. Ground-source heat pumps have been around longer and are more efficient, but they are typically more expensive to install. Air-source heat pumps have become widely available commercially only in the past few years, are relatively easy to install, and are typically much cheaper to operate than electric resistance heaters. Although some earlier models struggled to provide heat in below-freezing weather, many newer models are designed to operate to −18°C (0°F) or colder. Deploying heat pumps in superinsulated buildings (see the discussion of passive solar design later in this section) is one of the most easily identifiable, and most sensible, pathways for transitioning to an all-renewable energy system.

Solar Thermal

Solar water heaters are already common in many parts of the world. Indeed, according to the Renewables 2014 Global Status Report by the Renewable Energy Policy Network for the 21st Century (REN21), solar hot water capacity, at 330 GWh in 2013, was exceeded only by biopower generation in renewable energy capacity, with wind power a close third.[13] China leads with nearly 65 percent of solar thermal capacity followed by Europe with 20 percent.[14] In the United States and Canada, the principal application is for heating swimming pools. The main drawback with this energy source is simply that, especially in regions far from the equator, there are weeks or months during the year when solar heating has to be supplemented with gas or electric water heaters. Severe cold can create additional problems with freezing and breakage of pipes.

Solar plate collectors similar to ones used in water heaters can also be used to heat air. The use of water or air heated directly with sunlight (bypassing electricity) could be greatly expanded for some industrial applications, such as washing, sterilizing, drying, and baking, and in the paper and textile industries. The capital costs of deploying solar air and water heaters (and the energy embodied in them) would be far less than that entailed in photovoltaic panels or wind turbines used to make electricity, which then heats air or water. And in most applications, existing industrial machinery and distribution infrastructure could still be employed, with only the energy source needing replacement.

The potential for solar heat in industrial processes is perhaps even larger than that for households.[15] Where medium temperatures of 100°C to 400°C (212°F–752°F) are needed, solar concentrator technologies now used for electricity production could be adapted.[16] The main challenges would lie in either adapting production schedules to the sunniest times or finding ways to store thermal energy.

Geothermal

As discussed in chapter 3, high-quality geothermal energy is currently available only in regions where tectonic plates meet and volcanic and seismic activity are common, though low-temperature geothermal direct heat can be tapped nearly anywhere on Earth by digging a few meters down and installing a tube system connected to a heat pump (strictly speaking, this counts as stored solar energy).

Where geothermal energy is available and is close to an urban area, it can be used in district heating systems. Geothermal district heating (GeoDH) markets are developing throughout Europe, notably in Paris, Munich, and Hungary, with systems under consideration in the Netherlands, Madrid, and Newcastle (UK). It has been estimated that by 2020, most EU nations will have at least one GeoDH installation.[17] In the United States, the first GeoDH system was constructed in the 1890s in Boise, Idaho, but growth in this technology has been very slow. There are currently only twenty-one operating GeoDH systems in the country, with a combined capacity of about 100 MW thermal. China has deployed hybrid heat pump systems combining solar thermal with geothermal heat pumps.[18]

While the temperatures obtainable from geothermal sources are not high enough for industrial processes like steel and cement making, they are perfectly suited to low-temperature applications already discussed.

Insulation and Passive Solar Design

An important strategy in eliminating the need for fossil fuels to heat buildings will be to reduce the need for heating and cooling by designing and constructing buildings for greater energy efficiency. In Germany, thousands of structures have been designed according to the “passive house” (German: passivhaus) standard; these homes and commercial or public buildings typically require only a small fraction—often only 5 or 10 percent—of the energy used to heat and cool similarly sized conventional structures.[19]

Echo Haven green community in Calgary, Alberta Photo David Dodge, Green Energy Futures
The EchoHaven community in Calgary, Canada, includes energy-efficient homes, including with passive house and net-zero design. (Credit: (cc-by-nc-sa) David Dodge, via flickr.)

Passive solar heating design entails three primary features: glazing for capturing sunlight, Trombe walls and other ways of storing heat, and insulation to maintain relatively constant temperatures. Important factors include orientation of the long side of the building toward the sun and the appropriate sizing of the mass required to retain and slowly release accumulated heat after the sun sets. Other passive uses of sunlight in buildings include daylighting and even solar cooling.

Depending on the study, passive solar homes cost less than, the same as, or up to 10 percent more than other custom homes; however, even in the latter case the extra cost will eventually pay for itself in energy savings. A passive solar building can provide only heat for its occupants, not electricity, which is a different technology; but if these techniques were used on all new buildings in climates that require heating, passive systems could go a long way toward replacing space heat from fossil fuels. Incorporating passive solar technologies into the design of a new home is generally cheaper than retrofitting them onto an existing home. Passive solar buildings, in contrast to buildings with artificial lighting, also provide a healthier, more productive work environment.

Limitations of passive solar heating include geographic location (clouds and colder climates make solar heating less effective), and the need to seal the house envelope to reduce air leaks, which increases the chance that pollutants will become trapped inside. The heat-collecting, equator-facing side of the house needs good solar exposure in the winter, which may require spacing houses farther apart and using more land than would otherwise be the case.

Fossil Fuels for Plastics, Chemicals, and Other Materials

Some readers may judge it to be outside the scope of this book to discuss nonenergy uses of fossil fuels as feedstocks for plastics, fertilizers, pharmaceuticals, pesticides, road-paving asphalt, sealing tar, paints, inks, dyes, lubricants, solvents, paraffin, synthetic rubber for tires, and so forth. However, fossil fuels employed for these purposes are still subject to depletion, and in most instances still ultimately contribute to greenhouse gas emissions or local environmental pollution. Thus, if we wish to properly conduct an “all-renewable future” thought exercise, we should take these nonenergy uses of coal, oil, and gas into account.

Total nonenergy use of fossil fuels (including the energy used to process the feedstock in products), amounted to approximately 808.6 million metric tons of oil equivalent (Mtoe) in 2012. This accounts for 7.4 percent of total fossil fuel consumption of 10,927 Mtoe .[20] The products produced from these fossil fuels are essential to agriculture, transportation, health care, and manufacturing; thus in many instances their importance to society may be far out of proportion to their energy footprint.

With regard to each of these materials, we must ask two questions: (1) How substitutable are fossil fuels in its production? and (2) Can this material be substituted with something else not derived from coal, oil, or natural gas? The list of fossil-fuel-based materials is quite long, and the authors of this report did not have the time or resources to make an exhaustive investigation. What follows is a highly selective exploration of just a few examples.

Plastics

Conventional plastics consist of a wide range of synthetic or semisynthetic organic chemicals that are malleable and moldable, including polyester, polyethylene, polyvinyl chloride (PVC), polyamide (nylon), polypropylene, polystyrene, polycarbonate, and polyurethane. They are typically derived from fossil fuels using processes involving heat (usually supplied by more fossil fuels) to yield specific molecules with desired qualities.

In recent years the chemical industry has devoted increasing effort to the production of bioplastics made from biomass sources, including vegetable fats and oils, cornstarch, pea starch, and microorganisms. Some bioplastics are designed to biodegrade, so that they can be composted (though they often break down rather slowly). These alternative plastics are suitable for making disposable items, such as packaging, cutlery, bowls, and straws; they are also often used for bags, trays, fruit and vegetable containers, egg cartons, meat packaging, and bottling for soft drinks and dairy products. Thermoplastic starch currently accounts for half the bioplastics market. Other types include cellulose bioplastics (cellulose esters, including cellulose acetate and nitrocellulose and their derivatives, such as celluloid); polylactic acid (PLA), is a transparent plastic produced from corn or dextrose; poly-3-hydroxybutyrate (PHB), a polyester produced by certain bacteria processing glucose, cornstarch, or wastewater; and polyethylene derived from ethanol.

Compared to conventional plastics, bioplastics require less fossil fuel for their production and introduce fewer net greenhouse emissions if they biodegrade. They also result in less hazardous waste than conventional plastics, which persist in the environment for centuries.

However, fossil fuels are often still used as a source of materials and energy in the production of bioplastics. In our current industrial agriculture regime, petroleum and natural gas are used to power farm machinery, to irrigate crops, to produce fertilizers and pesticides, to transport crops to processing plants, and to process crops. The production processes for bioplastics also require heat and fuels for machinery, and these are usually supplied by fossil fuels. Further, producing bioplastics as well as biofuels in large quantities could accelerate deforestation and soil erosion and exacerbate water shortages.

Bioplastics production capacity stands at 1.7 million metric tons per year, still a small fraction of the total production of all plastics globally, which in 2013 reached 299 million metric tons.[21]

Fertilizer

Nitrogen (ammonia-based) fertilizer is produced using the Haber–Bosch process, usually employing natural gas as feedstock—though China, the world’s largest fertilizer producer, primarily relies on coal as feedstock. The importance of this supplement to modern industrial agriculture can hardly be overstated. Over a hundred million tons of nitrogen fertilizer are applied annually around the globe; without it, Earth’s soil might not be able to provide over seven billion humans the food they now consume. Indeed, almost half of the nitrogen found in a typical human’s muscle and organ tissue originated in the Haber–Bosch process.[22]

In fertilizer production, while natural gas or coal is typically used both as a source of hydrogen to bind with atmospheric nitrogen and as energy for the process, hydrogen can be derived from other sources, including hydrolysis from water using electricity; electricity could also power the production process. Thus renewable energy–based fertilizer is chemically feasible—though it would be more costly to produce (unless and until natural gas and coal prices soar far higher than their current levels).

It is also possible to substantially reduce or even eliminate chemical fertilizer application using organic agriculture methods. Crop rotation can help with maintaining nitrogen levels, and simply planting a cover crop after the fall harvest significantly reduces nitrogen leaching while cutting down on soil erosion. Meanwhile, introducing nitrogen-fixing leguminous crops into the rotation cycle replaces nitrogen. Other substitution strategies could include broader and more effective use of animal and human manures (as civilizations did for millennia before the advent of synthetic fertilizers).

Cleverly designed polycultures that don’t require synthetic fertilizer can sustainably outproduce synthetic-fertilizer-dependent monocultures on small and large farms, when counting total combined yields.[23] Further, mixing crops and reconnecting crop and livestock production consistently makes more efficient use of land, nutrients, and energy. However, these strategies usually require more labor and more farmer expertise. Thus a renewable energy future will likely entail more expensive natural fertilizers, more farmers as a proportion of the overall population, and more locale-based education for farmers in the use of organic production methods.

Paints

The main functional constituents of paints include binders, solvents, and pigments. Most modern paints are entirely made of, or with the use of, fossil fuels. For example, typical binders include synthetic or natural resins, such as alkyds, acrylics, vinyl-acrylics, vinyl acetate/ethylene, polyurethanes, polyesters, melamine resins, epoxy, or oils. For water-based paints, the solvent is water; however, for oil-based paints, solvents may include alcohols, ketones, petroleum distillate, esters, and glycol ethers. Pigments fall into two categories: natural pigments, including clays, calcium carbonate, mica, silicas, and talcs; and synthetics, including engineered molecules, calcined clays, blanc fixe, precipitated calcium carbonate, and synthetic pyrogenic silicas. Hiding pigments, which make paint opaque and protect it from ultraviolet light, include titanium dioxide, phthalo blue, and red iron oxide. Exterior paints contain fungicides, again made from, and using, fossil fuels.

Recent years have seen a dramatically increasing market share for ecofriendly, low-volatile organic chemical, and organic paints, which do away with fossil fuel–based solvents. However, these are typically still latex paints that use synthetic polymers, such as acrylic, vinyl acrylic, and styrene acrylic, as binders. Truly organic latex paints—in which the binders are produced from plant-based biochemicals, and fossil fuels are not used to power the production process—are feasible, though the authors were unable to confirm that any company currently produces them. For examples of paints that are truly free of fossil fuels, it is probably necessary to look to the era prior to organic chemistry. Paints made from organic flaxseed and linseed oil were used for centuries in Europe, while milk paint—made with milk protein (called casein) and lime—was the interior paint of choice in colonial America.

Asphalt

Nearly all paved roads are currently built using asphalt, a sticky, highly viscous or semisolid form of petroleum. A single kilometer of roadway typically requires roughly 320 barrels of oil (most of it in the form of asphalt) for its construction.[24] It is difficult to imagine how modern industrial society could operate without its ubiquitous road systems, yet our current roads are made from a depleting, nonrenewable material; contribute to climate change; and release toxic gases both during the construction phase and throughout their lifetimes.

Paving with concrete is an obvious alternative, and it is much longer lasting. However, we have already explored the energy intensity of current cement production and the difficulties likely to be encountered in redesigning the process to use renewable energy.

An alternative road-building material has been proposed in the form of a “sandstone” road surface produced by combining sand with a specific type of bacteria. Designers Thomas Kosbau and Andrew Wetzler won the green design competition in the 2010 Incheon International Design Awards (Incheon, South Korea) for their proposed biological substitute to asphalt, claiming that it could be produced at lower cost, while offering similar performance characteristics as a paving material. Sand is spread and compacted on a road surface then sprayed with a Sporosarcina pasteurii (formerly Bacillus pasteurii) solution; the microbes act to bind the sand into a tough material that is intended to sustain heavy traffic.[25]

Kosbau and Wexler’s alternative road-paving material gained some publicity in 2010. The authors of this book were unable to discover whether or where their invention has undergone demonstration and performance testing on roads, but the same approach of using the microbial binder has since been tested for making building blocks and bricks[26] and is being investigated by the National Aeronautics and Space Administration (NASA) for use in constructing building blocks on Mars.[27] Until real-world commercialization occurs, it would be unwise to consider the “renewable paving” problem solved.

It is worth noting that, in a world of reduced mobility, the need for paving may also be significantly reduced.

Lubricants

Only a small proportion of overall petroleum production is diverted to the making of lubricants, but without these substances all the machines in the world with moving parts would soon grind to a standstill (friction is as unavoidable as corrosion). The properties of petroleum lubricants (high temperature stability, low viscosity breakdown, oxidative resistance) are impossible to match with vegetable oils.

Biobased lubricants are currently available on the market, but their manufacturing process is largely unclear owing to proprietary formulations. Most are based on vegetable oil base stock, which can be chemically, thermally, or structurally altered to improve performance, and all contain a range of additives, such as detergents, pour point depressants, viscosity index improvers, and rust inhibitors, to match the performance of petroleum-based lubricants in this area. Nonetheless, owing to the fundamental chemistry of vegetable oil base stock, biobased lubricants remain deficient in terms of storage stability, thermal oxidative stability, low-temperature properties, corrosion protection, and hydrolytic breakdown, thus reducing their potential scope of application.[28]

*          *          *

In this section we have surveyed only five examples of nonenergy uses of fossil fuels; however, they are crucial ones. They suggest that, in principle, current materials that rely on fossil fuels for feedstocks can be substituted, though often with a sacrifice in terms of higher cost or reduced functionality. More research and development, as well as wider commercial deployment, are needed. It also bears noting that, in instances where materials themselves have fossil fuel-free substitutes, the production processes for these substitute materials often employ fossil fuels for transportation or as a heat source.

Summary: Where’s Our Stuff?

This chapter discussed some easier and some harder ways to eliminate fossil fuels. The easier ways include heating buildings with air- and ground-source heat pumps, and heating water with solar collectors. The harder ways include making metals, cement, plastics, fertilizers, and roads without oil, coal, or natural gas.

As we noted, electric kilns and solar furnaces already exist, though they are not currently used for large-scale production of pig iron or cement. However, using these technologies to produce what amounts to the material scaffolding of our industrial society would probably entail much higher costs than industry is accustomed to. Further, each industrial sector faces enormous costs in process redesign and in construction of new facilities to enable the use of renewable energy. These costs will be passed along in the prices of the output products.

We also touched upon the fact that current manufacturing processes for solar and wind energy technologies depend on high-temperature industrial processes currently fueled by oil, coal, and natural gas. Again, alternative ways of producing this heat are feasible—but the result would be higher-cost solar and wind power. We will further explore the current dependency of renewable technologies on continued fossil fuel consumption in the next chapter.

In principle, most of the problems we have identified are solvable—but at a cost and with serious questions regarding scale. A fully renewable energy future will entail higher costs for building and maintaining infrastructure, and the scale at which manufacturing can take place and infrastructure can be built using only renewable energy is highly uncertain. Without a massive mandatory program, the transition will take decades, and even with such a program we are likely to end up with a different kind of economy in which goods that incorporate metals—and infrastructure that involves steel and concrete—are more expensive and rare.

With plastics and chemicals, again substitution is possible in principle, at least in many instances. And once again the issues are cost, scale, and rate, along with tradeoffs (in some cases) of practical utility. There are no absolute barriers to a 100 percent renewable energy economy. But, as we have noted, it seems likely to be a smaller, slower, and more localized economy than our current one. Rather than a highly mobile consumer economy in which citizens are encouraged to buy as many goods as possible, and in which manufacturers pursue a strategy of planned obsolescence in order to encourage consumption, it will likely be one in which it is necessary to make goods that last longer, and to promote reuse and repair of older goods.

 

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