Lec14

* Introductory Environment Science Lecture 14 Further Topics in Environment Science: Global Warming Revisited New Energy Technologies: Hydrogen, Fuel cells, Batteries & CO2 Sequestration Sewage Treatment and Waste Disposal Footprint * Global Warming Revisited: Global Dimming Between 1950s and 1990s, global irradiance at Earth’s surface, i.e. intensity of sun’s radiation (in W / m2), has decreased but trend has reversed Particulate matters (soot) and sulfur aerosols might be root cause (dirty coal; introduction of scrubbers for coal power plants throughout 1980s-1990s in most European countries; collapse of Communism); particles nuclei for cloud droplets; increase in smaller droplet amount -> reflects sun light Estimated to be as much as 10% (regional) Evidence: Pan evaporation & air traffic (9/11) Reason for some major droughts? Change in intensity changes amount of water vapor in air, i.e. hydrological cycle and clouds Another reason for recent global warming? What will be repercussions of China’s coal fired power plants? A solution to global warming? http://video.google.com/videoplay?docid=-2058273530743771382 * Global Warming Revisited: CO2 Sinks There are 2 natural CO2 sinks: Oceans Plants and soil Oceans adsorb CO2 until they are at equilibrium, i.e. They represent the largest sink. How long does it take to reach equilibrium? We have adsorption at surface and mixing (convection, organic matter) in vast deep ocean. What will happen as T increases: Generally, we find We might face yet another positive feedback mechanism! However, adsorption leads to acidification. Plankton growth? * Global Warming Revisited: Feedback Mechanisms & Nonlinear Models How long does it take for Earth to reach T steady state? 20 years? There are many feedback mechanisms to regulate CO2 concentration and/or temperature. Some are positive and some are negative feedback mechanisms. They are not fully understood and it is unclear which will dominate. Moreover, climate models are nonlinear and forecasting sensitive towards parameters and initial conditons. Examples: Albedo: Positive feedback? CO2 sinks (oceans, forests,…): Positive feedback? Plankton and plants: Negative feedback? Clouds: Negative feedback? * New Energy Technologies: Carbon Sequestration Carbon Capture and Storage (CCS): Process of capturing CO2 emissions from large emitters (oil, gas or coal-fired power plants) and storing these long term in some form Reservoirs: Depleted oil or gas fields (increases yield), saline formations (e.g. Germany), deep oceans There are only 3 projects world-wide up and running (Norway, US-Canada, Germany); 5 more (or so) planned AB tar sands might also move towards CCS Capture and storage requires energy and reduces plant efficiency by 5-20%; energy use up by 10-40%, energy costs up by 30-60%; NOx increases! Retrofitting costly and inefficient -> China! Storage reservoirs might suffice >1 century Carbon tax could pay for technology Extensive pipeline system may be needed Conversion will take decades * New Energy Technologies: Hydrogen vs. Batteries As we begin to decline in fossil fuel consumption, what will replace ICEs and fossil fuel power plants? Two options: Batteries Hydrogen fuel cells In both cases, we need to create electricity/energy to either recharge batteries or produce hydrogen. What is the better option? Overall efficiency (well-to-wheel analysis) Convenience Safety Costs Reliability * Hydrogen: Some Challenges Platinum catalyst: R.H. Borgwardt, Trans. Res. D, Vol. 6, 199-207 (2001): 1) Limited availability of Pt 2) Transition period of 30 years to replace ICE vehicles not feasible; 75-100 years more realistic 3) Pt demand for US auto fleet alone about 48% of world production 4) Pt production must increase dramatically to meet demands 5) Price of Pt might skyrocket due to immense demand => An alternative catalyst is essential! * Hydrogen Production & Storage Where does all the hydrogen come from? A real alternative is based on renewables (and possibly nuclear energy) Projected energy share of renewables in Western countries between 5% an 20% by 2020 If hydrogen is produced from coal, oil or natural gas (technology already existent), what to do with the carbon dioxide? Once produced, how to transport and store the hydrogen? Hydrogen released into atmosphere is a green house gas! * Costs Currently, costs of PEM fuel cell more than $1000/kW ICE: less than $50/kW Expensive components: platinum, membrane No mass production => low productivity => high costs => high price => no mass production Codes and standards are essential ICE and hybrid might remain viable alternatives for some time; difficult to compete with established technologies * Chicken & Egg Problem Hydrogen infrastructure must be built: pipelines, storage tanks, production facilities, refilling stations No hydrogen infrastructure => no fuel cell vehicles (or other fuel cell applications) => no hydrogen infrastructure Demand or supply first? How do we kick-start the hydrogen economy? Fleets, trucks, buses, ships first; major polluters with centralised refilling stations Tax incentives? Subsidies? * Well-to-Wheel Efficiency U. Bossel, Cogen. On-Site Power Prod., 55-59, 03-04/2004 S. and J. Eaves, J. Power Sources, Vol. 130, 208-212 (2004) 1) Energy efficiency of electric vehicles/electricity grid 2.5-4 times higher compared to hydrogen 2) Hydrogen not energy source but energy carrier * Well-to-Wheel Efficiency . * Sewage Treatment & Waste Disposal Did you know? Canada has 3 provincial capitals lacking sewage treatment facilities (beyond mechanical)? They are… EU legislation: Waste is manufacturers’ responsibility -> Packaging minimized, recycling maximized Residual waste a fraction of North America’s * Ecological Footprint Ecological footprint (EF) (Rees, Wackernagel, 1992) analysis attempts to measure human demand on the Earth's ecosystems and natural resources. It compares human consumption of natural resources with planet Earth's ecological capacity to regenerate them. It is an estimate of the amount of biologically productive land and sea area needed to regenerate (if possible) the resources a human population consumes and to absorb and render harmless the corresponding waste, given prevailing technology and current understanding. Using this assessment, it is possible to estimate how many planet Earths it would take to support humanity if everybody lived a given lifestyle. It’s controversial, yet useful. * Ecological Footprint 2003: World-wide approximately 1.8 hectares per capita. U.S. footprint per capita was 9.6 ha, Switzerland 5.1 gha per person, China 1.6 gha per person. Since 1980s, we exceeded carrying capacity of Earth. Compute your own footprint: http://zerofootprint.net/ * Ecological Footprint