Living On RenewabLES Views on Sustainability • Big Corporation • Oil Company • Broad Scale Large Companies • Sustainability often means staying in business and continuing to grow. • It has a financial sense to it. Oil Companies • Must have adequate reserves of oil to meet immediate needs, • But also have a stake in energy technology that will replace oil. “Big Picture” • Using technology to de-couple GDP from environmental damage. • i.e. Don’t subsidize pollution - make the environmental impact part of the real cost. • Let GDP grow, and reduce environmental damage, using market forces such as carbon trading. Anti-Free Market • Some think the free market is the CAUSE of the problem, not the solution. • i.e. the relentless drive for growth is responsible for the damage • Then sustainability means capping or reducing GDP. Social System Sustainable Development Survival and health Spatial of the physical and Industrial Ecology Scale bio-systems Industrial Relationship between System Design for Environment industrial and Design for the environment natural systems is the objective P C & P Intervention to limit Product System and control pollution Product lifetime Human lifetime Time Scale Civilization lifetime Natural? • Natural is a tricky term to use... •a : being in accordance with or determined by nature •b : having or constituting a classification based on features existing in nature • Are humans natural? If so, are their actions also natural? Natural • For the purposes of this discussion, we will assume natural means everything on the planet that is NOT associated with humans or human behavior. Ecological Metaphor • Based on observation that natural and industrial systems have certain features in common: • Resource transformation • Waste generation • Exist in ecosphere Resource transformation • Natural and industrial systems transform resources: materials and energy. • Nature through growth, industry through manufacturing • Plants: solar powered, carbon dioxide & minerals as raw materials • Animals: fueled by plants (or other animals), raw materials are plants, minerals or other animals. • Industrial: fueled by fossil fuels, raw materials from crust, oceans, and living things. Waste Generation • Natural system: metabolism and death; • • Recycled with 100% efficiency, uses solar power Industrial system: emissions, heat, and obsolesence. • Recycled at various levels (all <100%), uses nonrenewable energy to do so. Ecosphere • The ecosphere provides raw materials, primary resources, is a reservoir for waste, recycles waste, • Provides water and air, protection from UV radiation, etc. • Both systems exist within the ecosphere. • The natural system has demonstrated the ability to continue in equilibrium with the ecosphere. • The modern industrial system appears to be at risk here. • So, can we learn from the natural systems? Elements • Living things require carbon, nitrogen, hydrogen and oxygen. • These make carbohydrates, fats, and proteins • The carbon cycle, nitrogen cycle and hydrological cycle are important recycling routes for these critical elements. Carbon Cycle CO2 in Atmosphere photosynthesis decomposition Diffusion decomposition Animal metabolism photosynthesis Bacterial deposition Coal Aquatic biomass Calcereous deposits Oil, gas Limestone Elements • Industrial systems require many different elements most of the periodic table, including Carbon. • As in nature, processes that use carbon (coal, oil, gas...) return it to the atmosphere. However, the recovery rates of natural systems are not high enough to account for this. • Hence increase in carbon in the atmosphere since 1850. Carbon Cycle CO2 in Atmosphere Coal Limestone Oil, gas Natural Ecosystem • Uses few elements (mostly C, N, H, and O) • Is cyclic (materials circulate and transform continuously) • Subsystems (have evolved that use “waste” as food) • Closed Loop (no waste! see subsystems) • Indicator of wellbeing: Equilibrium Industrial System • Uses most of the periodic table • Is linear (transforms materials in products and waste) • Lack of subsystems (that use waste as a resource) • Open Loop (waste destroys sources they require) • Indicator of well being: Growth Differences • Industrial systems don’t have subsystems to handle waste, or the subsystems cannot handle the volume of waste produced. • Equilbrium vs. Growth • Growth generates increasing waste. • If growth is required, a method for addressing waste is also required. Wait a minute! • Natural systems in equilibrium? • There are fluctuations, but it is a stable, resilient system. Consider the CO2 curve we looked at increases lead to global changes that result in cooling that result in reduced CO2 that result in warming... • Cyclical is a form of equilibrium. Energy • The average power use in a developed country ranges between 4 and 14 kW per person. • This turns out to be about 120-450 GJ/year per person. Energy Consumption Sector Proportion (%) Transportatio n 32 Domestic 29 Industry 35 Other 4 Energy Sources • Only four sources of energy on earth: • Sun (wind, wave, hydro, photochemical, photoelectic) • Moon (tides) • Radioactive decay (geothermal heat, nuclear power) • Hydrocarbon fuel (really sun energy in fossilized form) Wind • Problem is power density (power per unit area that can be harvested). • On land, 2 W/m2. Offshore, about 3 W/m2. • • So how does this help in China? 7,012 m2 per person of land area in the whole country. So 14kW per person. • India: 2,590 m2 per person, so 5 kW per person. So basically we would have to cover the entire country in windmills to meet energy needs. • Solar Solar energy density varies with distance from the equator. Temperature regions can get up to 50 W/m2. • Solar thermal (50% efficiency) generates low grade heat (hot water). Useful for home use, but nothing else • PV (10-20%) so between 5 and 10 W/m2. Like wind, would need vast areas to meet human needs. • Flora (burn plants or ferment them, or eat them). Efficiency is about 1%. And we use extra energy to raise the plants, reducing effective efficiency to about 0.5%. Hydro • Power available depends on altitude and rainfall. • Mountain regions can provide 0.2 W/m2. • Not much, but these are generally uninhabited regions. Norway (66,000 m2/person) gets significant energy from hydro. • Waves Make waves move something (a barrier with a turbine). Energy is measured per length, not per area. As much as 40kW per meter. • It is difficult to capture the energy estimates are 1/3 efficiency. Need a long coast line for this to be an option. • If you have 50 million residents, would need 3,700 km to generate 1 kW/person. • Maintenance is a real issue. • Tidal Lunar power (tides) can generate about 3 W/m2. This is similar to wind power, but need coastal areas to capture. Geothermal • Heat conducts from core of the earth, augmented by unstable element decay in the crust. • To make electricity, we need at least 200C temperatures - which often means drilling 10 km. • Some places this is possible - Iceland, New Zealand, Yosemite... Conclusions? • No single renewable will do the job effectively. • Consider - if you cover a significant fraction of your country with solar panels, where do you live, grow food, etc.? • There is a significant cost in both initial construction and in maintenance. (2% of land based wind mills are destroyed by lightning each year, e.g.) • There is opposition from environmentalists about paving the country with machinery. • Abundant pollution-free energy is not available yet... Sustainable Materials • Sustainable material should be drawn from a source that is renewable: • • either grows as fast as we use it, or reverts to original state in an acceptable period of time It should be part of a cycle (like the natural cycles around C, N, H and O) Renewable Materials • Plants seem like a good choice - trees, bast fibers, seed hairs... • However today wood is harvested faster than it grows, so it is a diminishing resource. • Also the wood we use is cut, dried, chemically treated, transported... all with non-renewable resources. Recyclable Materials • If we can’t be truly renewable, can we be recyclable? At least, for all practical purposes... • Construction uses more materials than any other sector, so let’s look at that. Much construction happens in less developed countries where steel, concrete and brick are not easy to get. • This could provide us with some interesting ideas. Rammed Earth and Adobe • We have soil everywhere. • Mix it with straw or hair, some lime • Pressurize it (stomp it with boards) • You have rammed earth. • Straw bales are a waste product of modern agriculture. They can be used as building blocks, with a plaster or wood surface. • Low thermal conductivity, low heat capacity. • Reed has been used for thatched roofs for a long time - resistant to water, has a life of up to 80 years. Straw and Reed Hemp, Flax, Kenaf • These are fast growing grasses. The fibers (bast fibers) from the stems are strong and light. • Textiles can be made from them, as well as reinforced concrete (e.g. hempcrete). Hempcrete is about 75% by volume fiber. And it grows as fast as it is harvested. • Hempcrete sequesters about 0.3 kg carbon/kg Stone and Lime • OK, Stone isn’t renewable in any obvious sense. But it has a huge reserve except the “dressed” stone and marbles. • Field stone is readily available in large quantities and can make non-load bearing boundaries. • The use of lime mortar can make stone structures suitable for load carry. Quasi-Sustainable • The previous materials are nice, but not diverse enough to handle all situations. • Quasi-sustainable materials mean materials that are drawn from a large resource base, so large that even with exponential growth there is no risk of exhaustion. • Let’s look at the composition of the earth’s crust for guidance. Elements in the earth’s crust Element Weight % Oxygen 46.7 Silicon 27.7 Aluminum 8.1 Iron 5.1 Calcium 3.6 Sodium 2.8 Potassium 2.6 Magnesium 2.1 Titanium 0.6 Hydrogen 0.14 Phosphorous 0.13 Carbon 0.09 All others <1 Back to Energy • We have lots of materials in the crust - but it takes energy to extract them • Basically it is all about the energy. Exercise • Consider The Netherlands, with a population of about 16.5 million. If their average power draw per person is 6.7 kW, how much of the land would have to be taken up by wind turbines to meet the country’s energy needs? (Assume a load factor of 50%)