ISSUEWe already are the witnesses to some facts, which are occurring in our time:1. Some states are giving more subsidies for crop-production which are essential to bio-fuel production, than they are subsidizing farming, crop-production and growing edible plants.There are many appeals from United Nations which are pointing out the problem of food shortages and food production for poor countries. In addition, the EU is also conditioning their members to use 5-10% of bio-fuel in transportation. So, what is really happening really happening is that more and more of agricultural areas are used for crop-production for bio-fuels instead of using those areas to grow - food.2. Environmental pollution is a global issue, and because of it, urban areas are being deprived of clean air. Greenhouse gases and reduction of green, public spaces in cities, due to constant expansion and of building areas, are drastically reducing the quality of life in urban areas, and in fact, they are becoming hazardous.The issue here is: are we able to improve our life conditions with application of contemporary technologies refined in new ideas?Production of bio-fuels is certainly one of the options, but it has its drawbacks, which cannot be ignored. The task of replacing all conventional fossil fuels, used in transportation with bio-fuels would require vast agricultural areas to grow required amounts of plants and its crops to create enough bio-fuel.In relation to this issue we considered scientific facts, results, studies and calculations in creation of an architectural respond.OUR SOLUTIONOur solution is creation of utility towers used for production of bio fuel and city air recuperation. The idea is to place these towers on the very positions of existing petrol stations in cities. TYPOLOGY AND ADVANTAGESOne of the important aspect of this, vertical farming, is the choice of plants which would be grown and processed in these towers. Our research led us to conclusion that algae and bamboo would give the best production results; max. amount of bio-fuels per unit of surface (or spatial unit), also considering other factors, like cost of technologies required for cultivation and processing, growth rate, annual input-to-yield ratio, etc. Because of the high cellulose content of bamboo, large amounts of bio-ethanol (substitution for petroleum-derived gasoline) can be produced out of it, and by processing of algae further on, we get the large amounts of algal oil - the key ingredient to create biodiesel (substitution for conventional, petroleum-derived diesel). Apart from that, these plants aren't soil-dependant, which means that they can be grown in pools of water (process called hydroponics). Algae cultivation is possible in closed, water-filled glass tubes (photo-bio-reactors). These tubular panel systems require minimum space, in combination with optimal illumination enabling maximum floor and height area usage. Another important source of feedstock for bio-ethanol is organic waste, which is at first, converted to cellulosic biomass, and than it can be used to produce bio-ethanol. Organic waste from all over the town could be deposited in these towers, also reducing the amount of garbage needed to be deposited on garbage dumps. Distribution area is realized beneath the platform in which pipe systems of produced bio-fuels and oxygen are spread. This platform serves also as a green, public space and bridge, spanned over both sides of the road.In combination with the form of the tower and the platform beneath, the outer skin layer of the tower is presented with a symbolic eco parasite tubular system for growth of algae.An advantage of this type of plant cultivation is that water can easily be re-circulated, and actually nothing is wasted or lost. During the lifetime of these plants, they produce considerable amounts of oxygen, and not only that bio-fuels that are produced reduce the air pollution (because they are greenhouse gas free), but plants are injecting large amounts of oxygen into oxygen-deprived environments.By applying the Bio towers we would reduce the amount of valuable agricultural land used for production of bio-fuel plants as well as reduce transportation costs and related air pollution.This kind of crop production also has advantages over farming in open spaces, because it's not weather-dependant, and you can create artificial conditions which actually enhance the plant growth (conditions that can't be achieved in the natural environment). RESUMEWe envisioned this system and applied it to our immediate environment, cities in Croatia, but it is applicable to any urban area in the world. The visual identity of the towers is a symbol and result of their function.Beside the benefits of bio-fuel and oxygen production, we consider their architectural appearance as an added value primarily to the conscience of the city inhabitants.