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" Introducción Los números no mienten es un libro ecléctico que abarca desde las personas, las poblaciones y los países hasta el uso de la energía, la innovación técnica y las máquinas y dispositivos que definen nuestra civilización moderna. Por si eso fuera poco, concluye con varias observaciones sobre hechos relativos al suministro de alimentos y distintas opciones alimentarias, además del estado y la degradación del medioambiente. Estas son las grandes cuestiones que he abordado en mis libros desde los años setenta. Por encima de cualquier otra consideración, esta obra trata de que los hechos cuadren. Pero eso no es tan fácil como podría parecer: aunque la World Wide Web rebosa de números, demasiados de ellos son cantidades reutilizadas de procedencia desconocida, a menudo expresadas en dudosas unidades. Por ejemplo, el PIB francés en 2010 fue de 2,6 billones de dólares, pero ese valor ¿está dado en moneda corriente o constante?; la conversión de euros a dólares ¿se hizo empleando la tasa de cambio actual o la paridad del poder adquisitivo?; ¿cómo podríamos saberlo? Por el contrario, casi todas las cifras que aparecen aquí están sacadas de cuatro clases de fuentes primarias: estadísticas de ámbito mundial publicadas por organizaciones globales,[1] anuarios publicados por instituciones nacionales,[2] estadísticas históricas recopiladas por las agencias nacionales "
― Vaclav Smil , Numbers Don't Lie: 71 Things You Need to Know About the World
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" Opportunities for enhanced recycling remain great even in the case of paper and aluminum cans, the two materials whose recycling rates are the highest in all affluent countries (Japan's paper recycling may be the exception as it is already about as complete as is practical). Perhaps most notably, until 2008 paper was still the largest discarded material going into US landfills (almost 21% of the total mass, compared to nearly 17% for plastics), and although by 2010 it had fallen to just below plastic's share (16.2 vs 17.3%) the total mass of buried paper was still nearly 27 Mt/year (USEPA, 2011a): that is more than the annual production of all paper and paperboard in the same year in Germany (FAO, 2013). And while the mass of paper landfilled in the USA in 2010 was half of the total in 1990 (26.7 vs 52.5 Mt), during the same two decades the mass of discarded plastics rose by 70% and the total of buried polymers, 28.5 Mt, was greater than the combined annual production in Germany and France (Plastics Europe, 2012). Or another comparison: a destitute waste collector may spend a day collecting a mass of 1 kg of plastic shopping bags when rummaging the open garbage tips of Asia's megacities, while the USA buries nearly 80 000 t of plastic in its landfills every day. While in the USA only about 8% of discarded plastics were recovered in 2010 (with the rate ranging from 23% for PET (polyethylene terephthalate) bottles to less than1% for PP (polypropylene) waste), the EU's goal for 2020 is full diversion of plastic waste from landfills (EPRO, 2011). This would require a 50% increase of the 2010 recovery rate of 66%, roughly split between recycling and incineration for energy recovery. And, of course, waste recovery is not synonymous with recycling as significant shares of collected materials are not reused but landfilled (after volume reduction by shredding or compression). "
― Vaclav Smil , Making the Modern World: Materials and Dematerialization
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" Only three fundamental variables – mass (M), length (L), and time (T) – are needed to derive the units repeatedly encountered in energy studies. Area is obviously L2, and volume L3, mass density M/L3, speed L/T, acceleration (change of speed per unit of time) L/T2, and force, according to Newton’s second law of motion, ML/T2 (mass multiplied by acceleration). Energy is expended (work is done) when a force is exerted over a distance: energy’s dimensional formula is thus ML2/T2. "
― Vaclav Smil , Energy: A Beginner's Guide
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" Everybody is familiar with the standard names of SI units for length (meter, m), mass (kilogram, kg) and time (second, s) but degrees Kelvin (K) rather than Celsius are used to measure temperature; the ampere (A) is the unit of electric current, the mole (mol) quantifies the amount of substance and the candela (cd) the luminous intensity. More than twenty derived units, including all energy-related variables, have special names and symbols, many given in honor of leading scientists and engineers. The unit of force, kgm/s2 (kilogram-meter per second squared), is the newton (N): the application of 1 N can accelerate a mass of one kilogram by one meter per second each second. The unit of energy, the joule (J), is the force of one newton acting over a distance of one meter (kgm2/s2). Power, simply the energy flow per unit of time (kgm2/s3), is measured in watts (W): one watt equals one J/s and, conversely, energy then equals power 3 times, and hence one J is one watt-second. "
― Vaclav Smil , Energy: A Beginner's Guide
