Glycerol is a by-product of the production of biodiesel by transesterification, and constitutes 10% of the quantities of the oil used. Rather than discard the glycerol formed, some market needs to be found, as any value obtained from glycerol will go some way to reduce the cost of biodiesel. Initially glycerol was sold to the chemical and soap industries and was used to reduce the overall cost of biodiesel. The effect of glycerol prices on the cost of biodiesel is shown in Fig. 7.20. The rapid growth in biodiesel production has produced a glycerol surplus which has resulted in a drastic decrease in glycerol prices and the closing of glycerol-producing facilities by compa­nies such as Dow Chemicals and Procter and Gamble (Yazdani and Gonzalez, 2007). The price has dropped in the USA from US$0.25/lb in 2004 to US$0.025/lb in 2006. Therefore, alternative uses for glycerol need to be considered.

There are a number of potential uses for the excess glycerol and these are shown in Fig. 7.21. The simplest option is combustion as glycerol has a calorific value (16 MJ/kg). Glycerol can also act as a substrate for anaerobic digestion where it has been shown to stimulate biogas production. It can also be metabolized by some microalgae which can be used as a source of oil or used in anaerobic digestion.

Several microbial species such as Klebsiella pneumoniae and Citrobacter freundii can ferment glycerol to produce 1,3-propanediol (Mu et al., 2006; Yazdani and Gonzalez, 2007). 1,3-propanediol is used to manufacture polymers (polyesters), cosmet­ics, foods and lubricants. Another option is to convert the glycerol by etherification (Fig. 7.21) (Karinen and Krause, 2006) which is butoxy-1,2-propanediol which is another fuel. Etherification with isobutene in the presence of an acidic ion exchange resin pro­duces butoxy-1,2-propanediol which has a high octane number (122-128). Thus, this can be an alternative to methyl-tert-butyl ether (MTBE) which is used as an oxygenate. Glycerol has been shown to act as a substrate for citric acid synthesis with Yarrowia lipolytica (Papanikolaou et al., 2008). Glycerol has been blended with petrol using a third liquid, ethanol or propanol, to make the two miscible (Fernando et al., 2007). Finally, glycerol can be used as a substrate for the microbial production of plastics poly(3-hydroxybutyrate) PHB and poly(hydroxyalkanoates) PHA (Ashby et al., 2004).

0. 54

Conclusions

Biodiesel produced from plant oils, animal fats and waste cooking oils has been shown to be suitable for use in diesel engines and is currently being added to diesel as a 5% addition. The amount of biodiesel produced worldwide and in the EU is increasing but there are insufficient plant oils available to increase this addition to much more than 10%. If there is any more than a 10% addition, oil crops will begin to compromise food crops (Chapter 8, this volume). Therefore, the other sources of diesel replacements will have to be commercialized such as FT diesel, pyrolysis bio-oil and microalgae.

FT diesel is being produced from the fossil fuels coal and natural gas in two large plants. The plants have to be large to be economic, and even at the large scale, the fuel produced by the FT process is 2-4 times the cost of diesel. To be sustainable, the FT process needs to be run using biomass or waste materials and not fossil fuels. The large scale of the operation would introduce problems of transporting large quantities of biomass to these plants which would burn fuel. What is needed is an improvement in the costing of the FT process which is probable in gas cleaning and in the development of smaller economic units which could treat biomass locally rather than transport it many miles. Pyrolysis is somewhat simpler than the FT process but it would compete for biomass, and bio-oil needs processing before it can be used.

The last option is oil extracted from microalgae, which is at the development stage and so it is difficult to give costing accurately. However, microalgae as a source of biodiesel have a number of advantages over other plant-derived oils. Microalgae can be grown on non-agricultural land, can be grown in sea water, are more produc­tive than land plants and can be part of a CO2 sequestration system. Thus, they would appear to hold great promise for the future and there is considerable interest worldwide in microalgae.

Another potential future energy source is the methane hydrates. Methane hydrates are methane molecules encaged in a lattice of water molecules with a crystal structure of (CH4)5(H2O)75. Low temperature and high pressure induce hydrate formation, which when dissociated can release 164 times their own volume of methane. The amount of methane contained in the hydrates has been estimated at 21 x 1015 m3, equivalent to 11,000 Gt carbon (Kvenvolden, 1999). There are onshore (permafrost) and offshore (below 2000 m) deep sea hydrate deposits, and several countries have projects to exploit these (Lee and Holder, 2001; Glasby, 2003). Possible methods of exploitation are heating, depressurization and inhibitor injection to dissociate the hydrate. However, these methods do have disadvantages due to the instability of the hydrates, collection of the gas, instabil­ity of deep sea sediments and uncontrolled release of methane into the atmosphere.

Introduction

Greenhouse gases in the atmosphere are increasing, in particular carbon dioxide, from the steady values found before 1850. The increase in greenhouse gases appears to be due to the burning of fossil fuels, which has fuelled industrialization. In add­ition, the demands for energy are increasing as more countries become industrialized. If this increase in greenhouse gases continues unchecked, the consensus is that the world’s climate may be adversely affected (Stern, 2006; IPCC, 2007). The major sources of global energy are the fossil fuels, the supply of which is finite. Therefore, given these factors, considerable efforts have been made to develop non-fossil energy sources. The sources should be both sustainable and renewable, and reduce or elim­inate greenhouse gas emissions to the atmosphere.

Renewable energy means an energy source that can be continually replaced, such as solar energy and plant materials, where the energy is obtained from the sun or stored as a consequence of photosynthesis. However, there are some restrictions to renewable energy sources as these should not be depleted faster than the source can renew itself.

Sustainable development focuses on the long-term development to allow a switch from the use of finite resources to those which can be renewed. Sustainability has also become a political movement involving groups working to save the environment. Another term used for non-fossil energy sources is ‘carbon-neutral’ which means that either the energy production yields no carbon dioxide, such as solar and nuclear power, or the process only releases carbon dioxide previously fixed through photo­synthesis. In determining the carbon dioxide reduction for renewable energy sources, life-cycle analysis will determine the fossil fuel input into the production of the fuel and carbon dioxide produced. These must be taken into consideration when the car­bon dioxide savings are determined for some biofuels, which may be less than 100% carbon-neutral.

Urgent action is needed if the atmospheric greenhouse gases are to be stabilized at levels that would avoid damaging climate changes. This chapter covers the possible options available for the stabilization of greenhouse gases. In 2005, the world’s emis­sions of greenhouse gases were 33.7 Gt which included 26.5 Gt of carbon dioxide (Quadrelli and Peterson, 2007). Table 3.1 lists the top 25 carbon dioxide-producing countries.

The USA is the largest producer of carbon dioxide, but China is predicted to overtake the USA by 2025 (World Resources Institute, 2006). Neither country has signed the Kyoto Protocol. Both India and China have had rapid economic growth in the past few years and will account for 45% of new energy demand by 2030 (IEA, 2007). Coal is being used to generate electricity in both China and India which will increase greenhouse gas emissions more rapidly than other fossil fuels.

aCountries included in Annex 1, which also includes some countries with economies in transition. bGHG includes CO2, CH4, N2O, CFCs for the year 2000; CO2 data for 2000.

For some time the UK has been self-sufficient in supplies of oil and gas, but the sup­plies from the North Sea are declining and it is predicted that future supplies will have
to be imported. Figure 1.13 shows the predicted decline in oil and gas production from the North Sea, and Fig. 1.14 shows the predicted gas imports that will be needed by 2020.

It is clear that the UK will increasingly have to import liquid fuels. As the bulk of the reserves of oil are in the Middle East and gas reserves in Siberia, the imports will be coming from unstable areas where interruptions may occur at any time. In these conditions, any UK production of energy or fuel will go some way to secure the sup­ply of that energy.

The concerns on global warming started with the UN’s world’s first climate confer­ence in Geneva in 1979, where it was agreed to set up a panel to review the data on global warming. The panel set up was named the Intergovernmental Panel on Climate Change (IPCC), which was initiated in 1988 and its first report was published in 1990. The timeline of the UN conferences and the Kyoto Protocol is shown in Fig. 3.1. Throughout the period that the IPCC has gathered data, there have been sceptics who have dismissed global warming as natural variation. For this reason the IPCC reports have been cautious in coming to any conclusion.

In the first IPCC report, it was concluded that the planet was warming and that human activity was possibly responsible. In the second IPCC report, in 1995, it con­cluded that the balance of evidence indicated global warming was occurring. At the second United Nations Conference on Environment and Development (UNCED)

START IN 1979 WITH WORLD FIRST CLIMATE
CONFERENCE IN GENEVA

IPCC STARTED IN 1988

1988 TORONTO SCIENTIFIC CONFERENCE

1990 FIRST IPCC REPORT
Planet is warming and human
activity responsible

I

1992 SECOND ‘EARTH SUMMIT’ UNFCCC CONFERENCE IN
RIO DE JANEIRO

1995 SECOND IPCC REPORT
Balance of evidence suggest global warming
1995 COP-1 MEETING IN BERLIN

1997 COP-3 MEETING IN KYOTO WHERE THE ‘KYOTO PROTOCOL’
FORMULATED

5% reduction in 1990 values by 2010
1998 UNFCCC COP4 BUENOS AIRES
2001 THIRD IPCC REPORT
2002 THIRD ‘EARTH SUMMIT’ JOHANNESBURG

2004 UNFCCC COP-10 BUENOS AIRES
Russia ratifies Kyoto

2005 KYOTO IN FORCE

Fig. 3.1. Kyoto Protocol timeline.

‘Earth Summit’ in Rio de Janeiro in 1992, the convention, named the UN Framework Convention on Climate Change (UNFCCC), was adopted which came into force in 1994. At the Rio meeting, it was concluded that carbon dioxide emissions needed to be reduced, and a Conference of the Parties (COP) was set up to oversee this reduc­tion. A series of meetings of the COP to the UNFCCC have discussed the problems of global warming. Discussions by the developed countries started at COP 1 in Berlin, and after 2.5 years of negotiations the Kyoto Protocol was agreed at the COP 3 con­ference in Kyoto in 1997. Although 84 countries initially signed the Protocol many were reluctant to sign before the details were clear. To be put into effect the Protocol had to be ratified by the developed countries, which produce 55% of the global car­bon dioxide. To date some 182 countries have ratified the Protocol, and with Russia’s recent ratification the Kyoto Protocol came into operation in February 2005. Ratification means that countries in Annex 1, which are developed or with an econ­omy in transition to a developed state, have agreed to cap their emissions of green­house gases. The Protocol commits these countries to individual, legally binding

targets to limit or reduce greenhouse gas emissions. For example, carbon dioxide emissions were to be reduced by an average of 5.2% below 1990 levels by 2008-2012 and a reduction of 20% by 2010. For some of the countries reductions will need to be quite large as emissions have continued to rise between 1990 and the present.

Most of the members of the Organisation for Economic Cooperation and Development (OECD) plus the states of Central and Eastern Europe are included in Annex 1 (Fig. 3.2). Under the Kyoto Protocol, the EU 15 was to be regarded as a single unit with a target of 8% reduction, but each country was also assigned a sepa­rate value. For example, although the EU figure was 8%, Germany was set a target of 21% reduction and the UK 12.5%, whereas others had an increase such as Spain at +15%. Countries joining the EU later in 2004-2007 have been assigned their own individual Kyoto targets.

The Kyoto Protocol is essentially a ‘cap and trade’ system, which includes a flex­ible mechanism that allows the purchasing of greenhouse reductions from other countries. Trading is allowed under the control of the Clean Development Mechanism (CDM), which means that any greenhouse gas reduction scheme in non-Annex 1 countries will earn Carbon Credits which can be sold to Annex 1 countries. The trad­ing scheme was put into place because there were fears that the costs of emission reductions would be too expensive for Annex 1 countries and as an incentive for non­annex countries to reduce emissions. The EU created the EU Emissions Trading Scheme (EU ETS) and the UK its own voluntary scheme (UK ETS). Figure 3.2 gives the reduction in emissions agreed under the Kyoto Protocol by Annex 1 countries and the percentage change achieved by 2005. The changes in carbon dioxide emissions from three of the large producers not in the Kyoto Protocol are +15.8% for the USA, +47% for China and +55% for India. Recently India has ratified the Kyoto Protocol, and is now a member of the Annex 1 countries. The reason for the large increases in emissions from China and India is their rapid industrialization since the late 1990s.

The targets for the Kyoto Protocol are to be calculated as an average over a 5-year period. Progress in reduction in the three greenhouse gases — carbon dioxide, methane and nitrous oxide — will be measured against the values for 1990. The chlorofluoro — carbons (CFCs), another greenhouse gas, have been dealt with under the 1987 Montreal Protocol, where their use was banned.

Renewable energy means an energy source that can be continually replaced, such as solar energy and plant materials, where the energy is obtained from the sun during

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photosynthesis. However, to allow indefinite use, renewable sources should not be depleted faster than the source can renew itself.

There have been a number of definitions for sustainability. One definition was ‘development that meets the needs of the present without compromising the ability of future generations to meet their needs’ (Glasby, 2003). It has also been defined as ‘to prolong the productive use of our natural resources over time, while at the same time retaining the integrity of their bases, thereby enabling their continuity’ (de Paula and Cavalcanti, 2000).

Sustainable development focuses on the long term, using scientific developments to allow a switch from the use of finite resources to those which can be renewed. Sustainability has also become a political movement involving groups working to save the environment.

Another term used for non-fossil energy sources is ‘carbon-neutral’, which means that either the energy production yields no carbon dioxide, such as solar and nuclear power, or the process only releases carbon dioxide previously fixed in photosynthesis (Fig. 1.15). In determining the carbon dioxide reduction for renewable energy sources, life-cycle analysis will determine the fossil fuel input into the production of the fuel and carbon dioxide produced. These points must be taken into consideration when the carbon dioxide savings are determined, and when applied to biofuels many are less than 100% carbon-neutral.

Conclusions

It is clear that the world’s energy demand will continue to increase in developed coun­tries and more particularly in developing countries such as China and India. The pattern of fossil fuel use is also changing with coal being replaced with gas for electricity generation. At the same time, renewable sources of energy are being devel­oped, in particular biogas and wind power. It is clear that the supply of fossil fuels is finite, considering how it was produced, but the discussion centres around how long the stocks will last and the extent of the fossil fuel reserves. The world’s dependence on a constant supply of energy means that whatever the estimate of the fossil fuel reserves, renewable sources need to be introduced as rapidly as possible.

The objective of the UNFCCC is to stabilize greenhouse gases at an atmospheric level that would avoid damaging the environment completely and reduce further global warming. The Annex 1 countries are required to adopt climate change policies and measures to reduce emissions of greenhouse gases. The IPCC has developed a number of scenarios in order to predict carbon dioxide emissions by 2030. Some of these are shown in Fig. 3.3.

In the high growth scenario with no reduction in greenhouse gas emissions, carbon dioxide will reach 42 Gt/year by 2030, mainly from the economies of the USA, China, Russia and India reaching around 700 ppm carbon dioxide in the atmosphere. In the alternative scenario, where greenhouse gases are reduced, carbon dioxide emissions peak at 2012 and begin to decline after 2015. This would represent a final atmospheric car­bon dioxide concentration of 550 ppm which corresponds to a temperature rise of 3°C.

Fig. 3.3. Three scenarios for the stabilization of atmospheric carbon dioxide The high growth (♦); alternative scenario (■); 450 stabilization (▲). (Redrawn from IEA, 2007.)

This may be achieved by structural changes in the economy and changes to the fuels used in the largest emitting countries. The 450 ppm stabilization is the lowest in the IPCC scenarios, and requires a drop in carbon dioxide emissions to 23 Gt by 2030, which corresponds to a temperature change of 2.4°C. This would require con­siderable changes in both Annex 1 and non-annex countries, many of which would be costly.

As can be seen in Fig. 3.4, although many of the Annex 1 countries have reduced their greenhouse gas emissions, the global emissions have continued to rise since the Kyoto Protocol came into being.

It is clear that those developing nations with high emission levels will need to implement emission control if the atmospheric concentrations of greenhouse gases are to be stabilized.

Introduction

Weather and climate have profound effects on all forms of life on Earth, and the major influence on climate is the energy derived from sunlight. Weather has been defined as ‘the fluctuating state of the atmosphere in terms of temperature, wind, precipitation (rain, hail, and snow), clouds, fog and other conditions’ (IPCC, 1996). Climate refers to the mean values of the weather and its variation over time and posi­tion. Perhaps in simple terms, weather is the conditions experienced by the individual and climate is the conditions experienced by countries and other land areas. The atmospheric circulation and its interaction with large-scale ocean currents, land masses and the sun determine climate. The effect on climate is known as forcing, and the most important determinant is the sun.

The atmosphere is composed mainly of nitrogen (78%) and oxygen (20.95%) and has recognizable layers starting at the surface with the troposphere, followed by the stratosphere, mesosphere and thermosphere. The troposphere is the layer in which weather occurs and contains 90% of the gases that make up the atmosphere. In this layer there are a number of gases other than nitrogen and oxygen, but only present in trace amounts, which include carbon dioxide, methane, nitrous oxide and ozone. In addition to these gases, the atmosphere contains solid and liquid particles and clouds (water vapour). Ozone in the atmosphere is found in trace amounts at all levels but is at a maximum (8-10 ppm) in the stratosphere, known as the ozone layer. All these gases absorb and emit infrared radiation and are collectively known as the greenhouse gases (Table 2.1).

All the gases, except the chlorofluorocarbons (CFCs), can be formed in nature and the balance between their production and elimination ensures that the global temperature is constant and sufficient to maintain life on the planet. Water vapour, which is also a greenhouse gas, is the most variable and is not normally included with greenhouse gases.

About half the radiation which arrives from the sun is in the visible range (short wave, 400-700 nm) and the other half is made up of near infrared (1200-2500 nm) and ultraviolet (290-400 nm). The land surface, consisting of soil and vegetation, influences how much of the sunlight energy is adsorbed by the Earth’s surface and how much is returned to the atmosphere. Ice in the form of glaciers, snowfields and sea ice reflect radiation, whereas dark surfaces adsorb radiation.

The Earth’s surface temperature is considerably lower than the sun’s (14°C com­pared with 3000°C) and as a consequence it radiates any energy as infrared (Fig. 2.1). This is known as black body radiation. Some of the energy adsorbed by the Earth’s surface is lost by radiation into space. However, the loss of this infrared radiation is affected by the greenhouse gases. These gases absorb the radiation and direct some of it back to the Earth’s surface. The outcome of this return of energy to the surface is

Table 2.1. Greenhouse gasesa and their contribution to global warming (1980-1990). (Adapted from IPCC, 1996.)

that the average temperature of the Earth’s surface is 14°C rather than -19°C, which would be the case if all the radiated energy was lost into space (Figs 2.1 and 2.2). Some of the greenhouse gases are better at absorbing radiation than others and there­fore their effects are not directly linked to their atmospheric concentrations (Table 2.1). For example, methane is 21 times as efficient as carbon dioxide in adsorbing infrared radiation, but as the concentration of methane is 350 times less than carbon dioxide its contribution to global warming is 15% compared with carbon dioxide at 55% (Table 2.1). If the greenhouse gas concentration remains constant, the energy

Table 2.2. The effect of human activity on greenhouse gas levels.

input from the sun is balanced by the proportion lost by radiation and the global temperature remains stable.

In 2001 a number of directives were produced to encourage renewable energy sources. Directive 2001/77/EC set a target for each member state for the proportion of electricity produced from sustainable resources and later the ten new members also

Fig. 3.4. Global, Annex 1 and Kyoto target carbon dioxide emissions now and predicted in Gt. (From IEA, 2005a.)

set up national targets. Directive 2003/30/EC covered the promotion of biofuels for transport, and member states are permitted to reduce excise duties on biofuels (Directive 2003/96/EC).

Under what is considered an optimistic view, Table 3.2 shows the possible share of alternative fuels in the EU by 2020 (Demirbas, 2008). In this case, natural gas use increases until 2030-2040, after which it declines. Biofuels show a steady increase up to 2050, and over this time period hydrogen overtakes biofuels and replaces natural gas.

The climate system has remained relatively stable for at least 1000 years prior to the Industrial Revolution as measured by ice-core determinations. The atmosphere has maintained a balance between carbon dioxide fixed by photosynthesis in vegetation and soil and the production of carbon dioxide from the decomposition of biological materials and plant and animal respiration. In this balance the oceans have acted as

a large carbon dioxide sink, but the adsorption rate of carbon dioxide into the oceans is slow. Figure 2.3 shows the carbon dioxide flows between the oceans, forests, soil and atmosphere with the concentration held in these areas in gigatonnes (Gt — 109 t) of carbon dioxide.

Since the start of the Industrial Revolution, atmospheric concentrations of car­bon dioxide, methane and nitrogen oxides have all increased. The increases in carbon dioxide, methane and nitrous oxides appear to be due to human activities, as shown in Table 2.2. The reasons for this increase are the burning of fossil fuels, deforestation, agricultural activities and the introduction of CFCs. The burning of fossil fuels oil, coal and gas releases carbon dioxide trapped by plants and animals millions of years ago (Fig. 2.3). The overall pattern of greenhouse gas production worldwide is shown in Fig. 2.4, where the major source of carbon dioxide is energy utilization. Carbon dioxide is also produced with land use change such as deforestation and cultivation. The major source of methane and nitrous oxide is agriculture.

The term ‘global warming’ is not new as it was first coined by J. B. Fourier in 1827, and in 1860 J. H. Tyndall measured the heat adsorbed by carbon dioxide.

However, it was not until 1938 that G. Callender showed for the first time that the world’s temperature was increasing and, in 1957, that carbon dioxide could be the cause. In 1965, the US government first looked into the connection between atmos­pheric carbon dioxide increases and the burning of fossil fuels, which was confirmed at the 1979 World Climate Conference in Geneva.

A panel of experts was asked to study the effect of greenhouse gases on climate change by the United Nations. These invitations led to the introduction of the Intergovernmental Panel on Climate Change (IPCC) in 1988.

The IPCC in its report Climate Change 2007: The Physical Science Basis con­cluded from a number of observations that ‘warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level’.

There are a number of factors that can influence global warming in addition to greenhouse gas concentrations. One of the methods used to determine the effects of various factors, including the greenhouse gases, is to calculate their radiative forcing. Radiative forcing is a measure of the influence that a factor has on the world’s energy balance — both positive and negative (Table 2.3). The greenhouse gases have all positive radiative forcing values but aerosol and clouds reduce radiation reaching the surface, thus reducing global warming. This effect has been seen in cases where volcanic activity has deposited large amounts of dust into the atmosphere.

The main consequence of the build-up of greenhouse gases is the increase in global temperature (Fig. 2.5). The consequences of increases in greenhouse gases will be an increase in global temperature from 0.5 to 6.0°C, depending on the measures taken to reduce their emissions (IPCC, 1996).This is the most rapid change in global temperature for the last 10,000 years and will have a number of consequences and a number of scenarios put forward. A summary of the impact of climate change is given in Wuebbles et al. (1999) and Stern (2006), and this impact includes rise in sea level, loss of sea ice and glaciers, more extreme weather, and increases in desert areas

and drought. Thus, it can be concluded that ‘the balance of evidence suggests that there is discernable human influence on global climate’ (IPCC, 2007).

The melting of the sea ice and glaciers will increase sea level by 0.5 m which will directly affect people living in low-lying areas such as the delta regions of Egypt, China and Bangladesh where 6 million people live below the 1 m contour.

The evidence of global warming has come from a very wide range of studies rather than the monitoring of temperature, and some of the trends which have indi­cated global warming are as follows (IPCC, 2007):

• Global mean temperature in 1900-2000 increased by 0.6°C (Fig. 2.5).

• Lowest 8 km of atmosphere in 1979-2001 increased by 0.05°C.

• Ice and snow cover decreased by 10% in 1960-2001.

• Mean sea level has risen 0.1-0.2 m in 1900-2000.

• More frequent changes in the El Nino currents in 1970-2000.

• Increases in the number of cyclones.

• Decrease in glaciers by 10%.

• Decrease in sea ice in 1973-1994.

• Increase in growing season in 1981-1991 by 12 days.

• Increasing heavy rain in 1900-1994.

• Increase of 5-20% in Antarctic snowfall in 1980-2000.

The possible social and economic consequences of global warming as given by the Stern Report are shown in Fig. 2.6. It is clear that even if some of the predictions prove true, the production of greenhouse gases needs to be reduced as soon as possible.

Food

Rise in crop yields Rising number of people at

in high latitudes risk from hunger

Water

Small mountain glaciers Sea levels threaten

disappear worldwide major world cities

Significant changes in water supplies

Coral reef ecosystems damaged

Possible collapse of Amazon rainforest

Ecosystems