Transcript Slide 1
Ehrlich equation I=P•A•T Where I = environmental Impact P = Population A = affluence (GDP/person) T = Technology (impact/unit GDP) Problems with Ehrlich Eq. This model, which drove sustainability, has limitations. many developments in Few consider reduction in population as a desirable approach to sustainability Assumes technology is of the refining type – wherein resources are converted to energy. New technologies can increase efficiency and reduce resource impact, but this contradicts the Ehrlich equation. There is a need to re-write the Ehrlich equation and provide a richer model of human impact on earth’s resources. Population Population is growing For a local region, we usually consider the rate of population growth to be R = [Rb – Rd] + [Ri – Re] Where b = birth, d = death, i = immigation and e = emmigration Population Then, the population at some time t from the present is given as P = P0 eRt Rewriting the Ehrlich Equation Sustainability requires participation from the world population as a whole. This challenge is addressed in terms of average population response The goal is to shift resource consumption behavior. Shift in Resource Consumption Total Consumption To measure the total consumption of the population, the average (expected) value of the discrete distribution can be computed as: 8 c iPi i1 Total Consumption There are more than 8 categories of consumption – perhaps unique behavior per individual. Thus, consider the behavior as a continuous function rather than a discrete one. If the probability distribution function is f, then the continuous form of the expected value of the parameter, c, is now written E(c) c cf (c)dc Modelling Sustainability Sustainability can be viewed as the intent to make the expected value, E(c), as small as possible. With no outside constraints, f(c) may be chosen as an impulse function at the origin - no consumption at all! However this is not a realistic situation and we will introduce restrictions on the function, f(c). Sustainability Distribution Function We will assume that the distribution function f(c) is also dependent on a finite number of side constraints; E = education and awareness of individuals A = Cost. Availability of resource intensive materials, T2 = Renewable technologies, (note that T2 is used to differentiate renewable or environmentally friendly technologies from those denoted as T in the Ehrlich equation.) L = legislation that controls consumption Differential Sustainability Now we would like to find a function, f(c) that minimizes the average subject to the given side constraints. Taking the variation of the expected value equation results in c c f (c,E, A,T2,L....)dc Variation of Distribution Function The variation of the distribution function is given as: f f E E f A A f T2 T2 f L L Sensitivity of Distribution Function The variations on the right side of the equation indicate changes in the constraints, E, A, T2, and L and the partial derivatives represent the sensitivity of f(c), the number of individuals at a given level of consumption, to the changes in the respective constraints. For example, it is believed that ∂f/∂E is negative – as more people are educated and aware of sustainability issues, the function will be minimized. Only ∂f/∂A is considered positive in this research – increased availability of resources likely results in reduced sustainability. Implications Thus the following actions should result in a lowering of mean expected consumption: increase E (educate and raise awareness) decrease A (increase cost, reduce availability of resource intensive materials) increase T (increase renewable technologies) 2 increase L (create legislation to penalize consumption). Grand Objectives W1: Maintaining the existence of the human species W2: Maintaining the capacity for sustainable development and the stability of human systems W3: Maintaining the diversity of life W4: Maintaining the aesthetic richness of the planet W1: existence of the human species Global climate change Human organism damage Water availability and quality Resource depletion: fossil fuels Radionuclides W2: Sustainable development Water availability and quality Resource depletion: fossil fuels Resource depletion: non-fossil fuels Landfill exhaustion W3: biodiversity Water availability and quality Loss of biodiversity Stratospheric ozone depletion Acid deposition Thermal pollution Land use patterns W4: Aesthetic richness Smog Aesthetic degradation Oil spills Odor e.g. Climate Change Climate change ties into W1 and W3. Human activities that contribute to climate change include (not limited to) greenhouse gas emissions Greenhouse gas emissions come from (not exclusive): Energy use, ruminants, refrigeration, farming, transportation Climate Change Targeted activity for examination: Fossil fuel combustion Cement manufacture Rice cultivation Coal mining Ruminant population Waste treatment Biomass burning Emissions of CFC, HFC, N2O Loss of Biodiversity Targeted activity for examination: Loss of habitat Fragmentation of habitat Herbicide, pesticide use Discharge of toxins to surface waters Reduction of dissolved oxygen in surface waters Oil spills Depletion of water resources Industrial development in fragile ecosystems Stratospheric Ozone Depletion Targeted activity for examination: Emission of CFCs Emissions of HFCs Emissions of halons Emissions of nitrous oxides Human Organism Damage Targeted activity for examination: Emission of toxins to air Emission of toxins to water Emission of carcinogens to air Emission of carcinogens to water Emission of mutagens to air Emission of mutagens to water Emission of radioactive materials to air Emission of radioactive materials to water Disposition of toxins in landfills Disposition of carcinogens in landfills Disposition of mutagens in landfills Disposition of radioactive materials in landfills Depletion of water resources Water Availability and Quality Targeted activity for examination: Use of herbicides and pesticides Use of agricultural fertilizers Discharge of toxins to surface waters Discharge of carcinogens to surface waters Discharge of mutagens to surface waters Discharge of radioactive materials to surface waters Discharge of toxins to ground waters Discharge of carcinogens to ground waters Discharge of mutagens to ground waters Discharge of radioactive materials to ground waters Depletion of water resources Resource Depletion: Fossil Fuels Targeted activity for examination: Use of fossil fuels for energy Use of fossil fuels as feedstock Land Use Patterns Targeted activity for examination: Development of undisturbed land Emissions influencing sensitive ecosystems Restoration of disturbed land Approach Concern 1 Grand Objective Activity 1 Remedy 1 Activity 2 Remedy 2 Activity 3 Remedy 3 Concern 2 Concern 3 Remedy 4 Coffee Cups What’s better for the environment? Ceramic cup Paper cup Styrofoam cup Let’s simplify… Fossil fuel depletion Energy required to make the cup Energy required to reuse the cup -> Energy per usage Energy to make Material Mass of Cup (g/cup) Embodied energy Embodied energy of material per cup (MJ/kg) (MJ) Ceramic 290 48 14 Paper 8.3 66 0.55 Styrofoam 1.9 104 0.20 Energy to reuse Material Energy per wash (MJ/cup) Ceramic 0.18 Paper -- Styrofoam -- Assumed that cups are washed in an energy efficient dishwasher, electrical power, Canadian standards (1994). Note that dishwashers are more energy efficient than washing by hand (Dep’t of Energy). Energy per usage Paper: 0.55 MJ Styrofoam: 0.20 MJ Ceramic: [14 + (n-1) * 0.18 ]/n The more you use your ceramic cup, the more efficient it becomes. Energy per Use 14 Paper Energy per use (MJ) 12 Styrofoam Ceramic 10 8 6 4 2 0 0 10 20 Number of uses 30 40 Energy per use 1 0.9 Paper Styrofoam Ceramic Energy per use (MJ) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 20 40 60 Number of uses 80 100 Comparison To be more efficient than a paper cup, you must use your ceramic cup at least 39 times To be more efficient than a Styrofoam cup, you must use your ceramic cup at least 1,006 times. What’s missing ???