Ó 2014 Ecological Society of China. Published by Elsevier B.V.
Carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O)
are the three principal greenhouse gases (GHGs) in the atmo- sphere, and continuously increases in atmospheric concentrations of three GHGs are closely related to global climate change  . The studies on the GHG emissionsfromreservoirs in the last two decades indicated that hydroelectricity was not a green and clean energy as expected that no GHG is emitted from the reservoir sur- face [2–4] . In fact, reservoirs are also an important GHG source in the terrestrial ecosystems [5,6] . According to the natural belts that reservoirs located, the global reservoirs could be divided into trop- ical reservoirs (e.g., reservoirs in Brazil, French Guiana, and Laos) and temperate reservoirs (e.g., reservoirs in Canada, Switzerland, and China). The global warming potential (GWP) of the GHG emis- sions from Brazil’s reservoirs are amazing, which are even higher than that from thermal power plants with similar installed capac- ity  . For example, Curuá-Una Reservoir in Brazil emitted 3.6 times more GHGs than those would have been emitted by generating the same amount of electricity from oil  . However,
0.2 ± 0.15 mg CH 4 m -2 day -1 for all reservoirs, except
Lake Wohlen, which emitted 1.8 ± 0.9 mg CH 4 m -2
day -1 via surface diffusion. Though there were no signif- icant differences between methane emissionsfrom different altitudes, methane concentrations are lower in alpine reservoirs compared to lowland reservoirs. Factors like reservoir age, DOC input and latitude (equivalent to temperature) have been investigated by Barros et al. ( 2011 ). Temperature and organic matter input are presumably the most important factors for the decrease we found, while reservoir morphology of the predominantly steep and deep subalpine/alpine reservoirs could be an important factor as well. The higher dissolved methane concentrations and clearly visible oxygen gradients towards the sediment sug- gest high methane concentrations in the sediments of lowland reservoirs. This would lead to higher total methane emissions via bubble flux from the sediment (DelSontro et al. 2010 for Lake Wohlen) and in the end make lowland reservoirs sig- nificantly more important emitters of methane to the atmosphere. Further studies are needed to support this and determine up to which altitude bubble flux plays a role in reservoirs of the Alps.
such compound 3-nitrooxy propanol (3NOP) which reduced emissionsfrom lactating dairy cows by ~30% and had a positive benefit for liveweight gain. The economics and practicality of using such compounds, in particular the mode of delivery, will need to be confirmed but the development of a compound that brings about a substantial reduction in emissions, is animal friendly and appears to have a productivity benefit is a major breakthrough. Researchers in New Zealand and Australia have also been working on stimulating the ruminants’ own immune system to produce antibodies that can suppress the activity of methanogens. Success has been reported in vitro (Wedlock et al. 2013) but not so far in vivo. The mode of delivery, the promise of infrequent treatment and the potential applicability to all classes of livestock make this mitigation route highly attractive. However, it is technically challenging and progress has been slow since the initial idea emerged in the mid-1990s.
To monitor progress on emissions reduction goals, it is important to collect data regularly, record changes and strive to improve performance continuously. Moreover, understanding such data geospatially will help target emissions reduction efforts in areas of the city with the highest emissions or the greatest potential for cost-effective reductions. Besides provid- ing the basis for policies and programs, data could be used more effectively in Chicago and the region to identify the best opportunities to mitigate climate change. Ongoing data col- lection and evaluation will help identify mitigation programs with the most impact, and help evaluate whether limited resources are directed to the most cost-effective strategies.
in agreement with the findings of Zhu et al. (2014), who reported that seasonal CH 4 emissions are highly linked to water table fluctuations. The important effect of water table on CH 4 emission rates is in agreement with observations in other studies (Bridgham et al. 2006; Couwenberg et al. 2011; Le Mer and Roger 2001; Serrano-Silva et al. 2014). Common anaerobic conditions are expected to lower CO 2 emissions but increase those of CH 4 (Treat et al. 2015), but emissionsfrom aerobic soils will likely dominate the permafrost C feedback (Schadel et al. 2016). GHG Flux and SMB
Acetic acid (acetate = derivate of acetic acid) is very common in the environment and can undergo a dismutation reaction to produce CH4 and CO2 simultaneously. In many studies (Whiticar et al. 1986, Ferry 1992, Conrad 1999, Keller & Bridgham 2007), the general claim is made that most CH 4 originates from the methyl group of acetate and only a smaller pool originates from the reduction of CO2 with H2. The process of aceticlastic methanogenesis, i.e. the conversion of acetate to CH 4 and CO 2 , has not been studied as extensively as the reduction of CO 2 to CH 4 (autotrophic methanogenesis) (Ferry 1992, Keller & Bridgham 2007). Some studies report that aceticlastic methanogenesis is more important in fens (Keller & Bridgham 2007, Galand et al. 2010) whereas autotrophic methanogenesis is dominant in bogs (Duddleston et al. 2002, Horn et al. 2003). Keller & Bridgham (2007) attributed the dominance of aceticlastic methanogenesis during the growing season to high acetate concentrations due to the presence of root exudates, whereas the proportion of CH 4 production that originates from CO 2 reduction increases with depth as labile root exudates become less available. Liberation of CH 4 can occur from saturated peat horizons via diffusion, gas bubbles (ebullition) and by plant-mediated transport in vascular plants such as Phragmites or Carex (Bastviken et al. 2004, Lai 2009).
warming potential (310 times that of CO 2 (UNFCCC, 2004)) makes it a large contributor to GHG
The majority of research to date on GHG emissions resulting from the land application of manure has focused on liquid manure, even though more than two thirds of land applied with manure in Canada receives solid or composted manure (Statistics Canada, 2006). Thus, there exists a distinct need for research on emissionsfrom solid manure application. Another important element to consider is the impact of manure management systems, such as surface broadcasting or injection of manure, on GHG emissions. The injection or incorporation of manure into the soil has the potential to increase these GHG emissionsfrom manure spreading, which is an important consideration when attempting to assess agriculture’s contribution to a region’s total GHG emissions. With new plans and strategies being put in place to reduce global GHG emissions, it is important to carefully analyze emissions that result from new technologies or practices. There are very few comprehensive studies that have addressed the effect of subsurface application on GHG emissions, particularly for solid manure. Therefore, the objective of this research was to compare GHG emissions between liquid and solid manure and surface and subsurface
Please note that the numbers in Table 3 are estimates, and not actual values. Research has found using international emission factors to estimate nitrous oxide emissionsfrom the WA grain belt is not appropriate due to differences in nitrogen (N) fertiliser management, soil types and climate, and factors demonstrated to influence annual agriculture nitrous oxide emissions (Stehfest and Bouwman 2006). Studies in WA, have found the international default value for soil nitrous oxide emissions over estimated measured greenhousegas by 52 per cent in wheat (Barton et al., 2008a) and were 50 times greater than actual nitrous oxide emissions associated with growing and converting canola for biodiesel production and the burning of biodiesel (Farm Weekly 2011). A University of Western Australia (UWA) five year study looking at paddock based greenhouseemissions in WA wheat growth has changed the Australian nitrous oxide emissions standards used from one per cent of N fertiliser (IPCC values) to 0.1 per cent (Department of Climate Change and Energy Efficiency values) for Australian grain growers (Farm Weekly 2011). The values reported in Table 3 are from the Grains Greenhouse Accounting framework which is using IPCC values.
available to the denitrifiers. In addition, the increased contact with microbes due to injection of manure may promote N 2 O emissions in the short term, but rapid
decomposition beneath the soil surface may mean that fluxes a few days after application are reduced. Some studies that reported on the effect of application technique on GHG fluxes only measured fluxes one or two times after application (Lovanh et al., 2008, Sistani et al., 2008) while others continually monitored fluxes over the course of 2 to 18 weeks (Weslien et al., 1998, Perala et al., 2006, Flessa and Beese, 2000, Wulf et al., 2002b). Of the studies that measured cumulative losses over a longer period, only Wulf et al. (2002b) found that injection resulted in significantly higher GHG emissions on a field scale. Collecting continuous GHG flux data from sites over several weeks is labour- intensive and does not always provide further insight or ability to clearly distinguish treatment effects. Therefore, a model that simulates the environmental conditions and nutrient transformations after manure application may be a more efficient approach to the prediction of the effect of management practices on total GHG emissions.
Uncertainty can also be simply described using words, for example, on a verbal scale. Words can be adapted to any level of understanding, and for most, the message they convey can be easily remembered. Words are often used to convey the uncertainty of events, for example, weather forecasters might tell us that snow is likely, and health workers might tell us that smoking is very likely to damage our health. Words can be straightforward to understand, but the transfer of information from a numerical to a verbal scale inevitably loses information, and so the result may lack precision. This method of communicating uncertainty is primarily criticized because of its ambiguity and the fact that verbal information may be interpreted inconsistently by different individuals (Kloprogge et al., 2007; Spiegelhalter et al., 2011). In an attempt to overcome this, the IPCC (Mastrandrea et al., 2010) introduced a verbal scale in which particular ranges of probabilities correspond to ‘ calibrated phrases ’ , for example an event which is expected to occur with a probability of more than 99% is said to be ‘ virtually certain ’ . This scale is enhanced by some authors with the use of a traf ﬁ c light scheme colour code, whereby the most uncertain phrases are linked to red, and the least uncertain green (Table 1). The verbal scale has been criticized, as studies have shown that it is not always interpreted consistently (Budescu et al., 2009; Harris and Corner, 2011).
Consistent with evidence that part of revenues accruing from environmental taxes is issued to make environmental improvements (e.g. Brett and Keen 2000; Haibara, 2009; Do Valle et al., 2012) our results for GHG emissions are unambiguous. All co- eﬃcients (except for ecolabel licenses) are statistically significant at the 1% level and have the expected sign (a negative sign indicates a favorable eﬀect on the change of CO 2 (equivalent) emissionsfrom industrial processes). The main results showed that increasing energy taxes directly have a statistically significant and negative impact (-1.464***) on the change of CO 2 (equivalent) emissionsfrom industrial processes. This finding is in line with the studies (e.g. Clinch, 2002; Pezzey and Park, 1998; Corbacho, Cibils, and Lora, 2013) that environmental taxes directly contribute to the improve- ment of GHG and other emissions. The analysis showed that environmental taxes have an impact on the level of GHG emissions in industrial processes also indirectly, through environmental expenditures in industry (-3.325***). This indirect impact of environmental taxes signifies that direct spending on activities for prevention, reduc- tion and elimination of GHG emissions is extremely important for environmental im- provement. However, the role of direct impact of environmental taxes should not be overlooked because economic entities seek to reduce their tax burdens. In this context, the EU countries use diﬀerent economic and financial instruments for the protection of the environment, e.g. financial guarantees, environmental deposits, taxes and other forms of security, direct and indirect subsidies, and tax allowances. Especially the last two represent financial incentives and opportunities for polluters to take advantage of using advanced green technologies in order to reduce costs and improve competitive- ness by reducing energy and resource consumption, and thus contribute to lowering the total amount of GHG emissions. Such measures are usually more stimulating for polluters than taxation or sanctions. In this context, polluters partly avoid paying en- vironmental taxes and are entitled to subsidies.
Livestock production is a significant source of gaseous emissions, such as methane (CH4), nitrous oxide (N2O) and ammonia (NH3). Several studies have been published estimating livestocks’ contribution to the anthropogenic greenhousegasemissions. The indicated percentage of livestock worldwide was stated at 18% in an FAO study (FAO, 2006), within the EU the percentage was estimated at 9.1% by LEIP et al. (2010). However, there is a broad discussion about where to put the system border and ‘the importance of getting the numbers right’ (HERRERO et al., 2011). Emission factors on barn level are composed of the animals’ release and by the emission generation of the manure on floors and channels. There are several studies in the literature focusing on CH 4 emissionsfrom enteric fermentation (AGUERRE et al., 2011; DERNO et al., 2009; Ellis et al., 2007; GARNSWORTHY et al., 2012; PLACE et al., 2011; VAN ZIJDERVELD et al., 2011) whereas emissions at the barn level have been studied less thoroughly (Ngwabie et al., 2009; Samer et al., 2011; Wu et al., 2012). Furthermore, some studies may be limited to model/scale studies (AGUERRE et al., 2007; PEREIRA et al., 2011). The proportion of CH4 emissionsfrom manure is estimated to be about 20% for dairy cattle worldwide (FAO, 2006). Other authors reported a percentage of CH4 emissionsfrom manure of 7-27% (HINDRICHSEN et al., 2006; HINDRICHSEN et al., 2005; KÜLLING et al., 2002). The influence of floor design on CH4 emissions at barn level has been poorly studied. However, PEREIRA, et al. (2011) reported higher emissionsfrom solid floors than from slatted floors at all temperatures, but this investigation was performed as a scale-model study. PEREIRA et al. (2012) reported a positive correlation of CH4 release and temperature, and illustrated that CH4 emission from cattle excreta is increased with temperature up to a temperature of 25°C.
In addition to simulation studies, empirical comparisons of various neighborhoods have been used to suggest that higher density, mixed use, and transit-oriented communities are associated with increased shares of transit and pedestrian travel and reduced VMT. For example, a 1994 study of the San Francisco Bay Area households found that households in newer suburban communities had substantially higher vehicle trip generation rates, a higher proportion of drive alone trips, and a lower percentage of public transportation trips than households in traditional communities. 48 Similarly, a 1996 study that examined travel diaries of residents in three Seattle mixed-use neighborhoods concluded that the pedestrian share of work trips was 11.3 percent in mixed-use communities, as opposed to 3.6 percent in King County as a whole. 49 An analysis of odometer readings from 27 California communities suggested that residential density and access to public transportation were the two urban form factors that most reliably predicted household auto travel behavior, and that doubling residential density reduced annual auto mileage per capita by 20 percent. 50 Similarly, an analysis of trips reported in the 1990 National Personal Transportation Survey (NPTS) found that each doubling in density reduced VMT per capita by 28 percent over the entire urban range of densities. 51
consumption in the future than it is today, the potentials for changing the type of meat and reducing the meat consumption can be seen as rather overestimating the changes in emissions. There are reasons to assume that consumption of meat will not increase dramatically in the public kitchens because of awareness and also for economical reasons. There are also reasons to believe that the efficiency increase possibilities for meat and vegetarian food are different. Also the included food in these two studies differs in more aspects than meat and milk which further increases the uncertainty of utilizing the potentials in this thesis. These are just small uncertainties compared to what would happen if land use changes also were included while estimating emissionsfrom food consumption, which most likely would point out meat as even worse. The latter uncertainty could be lowered by only consuming locally produced meat. The fact that it from this thesis seems like the food consumption can be responsible for about 8,4 % of the estimated (top-down) total emissionsfrom the municipality of Gothenburg's public emissions stresses the fact that this is an important area to consider.
Wood and Paper data
Published data on wood products is sparse, an issue highlighted by the Waste and Resources Action Programme (WRAP) in 2006 and 2010 87 . Data used in this report for waste prevention is based on studiesfrom the USA, where production processes may not be representative of activity in the UK (e.g. different fuel mix to generate electricity). This data should therefore be viewed with caution. Data on different types of wood has been used in combination with information on the composition of wood waste in the UK 88 to provide a figure which represents a best estimate of the impact of a typical tonne of wood waste. Many trade associations publish data on the impact of manufacturing 100% primary and 100% recycled materials. However, for various reasons, the bodies representing paper and steel only produce industry average profile data, based on a particular recycling rate.
The overall CF model will include epistemic uncertainty depending on how well the system analyst knows the system under study and its sub-processes, but also a type of variability due to human behaviour. There will be differences in how single CF for milk is assessed even if the well-established and ISO standardised method of LCA and special guidelines, such as IDF (2010), for milk CF estimates are used (Crosson et al., 2011; de Vries & de Boer, 2010; Gerber et al., 2010; Thomassen et al., 2008). This is due to the individual methodological choices that have to be made in different studies, which will affect the outcome of the assessment. Methodological choices include how functional units are defined, where the system boundaries are drawn and what sub-models that are chosen when estimating the CF. Another methodological choice that can affect milk CF dramatically is how the emissions are allocated between milk and other co-products from the system, as clearly illustrated by Flysjö et al. (2011a) and Zehetmeier et al. (2013). The large impact that methodological choices can have on the outcome of CF calculations clearly suggests that milk CF values should not be compared unless estimated uniformly (Paper I). For the same reason, it is also important to have high transparency in CF estimates.
Road pricing schemes can be used to charge road users and encourage more efficient use of the infrastructure and lower levels of pollution. The government published a Green Paper on motorway charging in May 1993 (Department of Transport, Scottish Office and Welsh Office, 1993). This considered alternative charging schemes for motorway traffic, including conventional tolling with toll- booths (which was rejected), a permit system and electronic meters. A number of alternative charging rates per mile were also considered. Although the document made some estimates of the likely diversion to other roads, it did not evaluate the costs of such diversion. However, later studies on economic disbenefits of traffic diversion in five area assessments conducted by the Department of Transport were reviewed by the House of Commons Transport Committee in its 1994 report, Charging for the Use of Motorways. The MPs concluded that `These results, based on the Department’s own procedures and computer models, suggest that current Government proposals may not meet the environmental and efficiency policy objectives set out in the Green Paper’ (House of Commons Transport Committee, 1994, para. 181).
In the crop studies (Papers I and II), a comparison was made between two different crops grown in the same field or adjacent fields at each site. The soil type (parent material of the organic soil), peat depth, drainage intensity (same distance from drainage ditch) and weather conditions were similar for both crops, and only the crop and its associated management differed. Figure 5 shows some examples for four of the sites concerned. The crops grown were divided into three main groups, grassland, cereals and row crops, since subsidence data are often presented separately for these three groups. The grasslands were a mixture of grass, e.g. timothy (Phleum pratense), except for the lawn grass, which contained meadow grass (Poa pratensis) and red fescue (Festuca rubra). The cereals were: oats (Avena sativa), barley (Hordeum vulgare), spring oilseed rape (Brassica napus), spring wheat (Triticum aestivum) and spring triticale (Triticum aestivum/Secale cereale). The row crops were: carrot (Daucus carota), potato (Solanum tuberosum) and parsnip (Pastinaca sativa).
This study is the lone experiment investigating the effects of tillage and CC rotations on GHG emissions and crop yields in the state of Illinois to date; likewise, this is one of few of its kind in the Midwest region. Establishment of CC species in the fall of 2013 was poor and stand counts were negligible for all species and were not reported; lower than average temperatures and precipitation (Fig. 4.1) likely caused the lack of CC stand in the fall of 2013. A similar weather pattern occurred in fall 2014 resulting in a low CC stand count. Due to the low establishment of CC species in the fall, subsequent spring biomass was negatively affected. Temperatures in January, February, and March of 2014 were abnormally cold and the only CC species to produce spring biomass was CcrShv (Table 4.4). In a review of other studies in the Midwest, Appelgate et al. (2017) found that rye species accounted for more than 79% of the spring biomass accumulation due to its ability to survive most winters in this region. The CrdSrd rotation was not expected to over-winter as is common for that species. Similar to 2014, cold temperatures in January, February, and March of 2015 impeded spring biomass growth and was very low; however, CarSar and CrpSrp did survive the winter as did CcrShv again. Due to a lack of cold tolerance, Appelgate et al. (2017) found that rape, oat, and radish have limited potential as CC species in the Midwest due to high rates of winterkill (Appelgate et al., 2017). In addition, at the same site, Dozier et al. (2017) concluded that the seeding method coupled with poor fall growing conditions was likely the reasoning for the poor fall CC establishment.
cussions about this issue show that there is a lack of solid data. The project "Climate effects and sustainability of organic and conventional farming systems - examination in a network of pilot farms" aims to attain more precise information. A total of 40 conventional and 40 orga- nic farms in Germany are compared in this project. Half of the farm pairs are dairy systems; they are located as organic/conventional pairs in regions with equal soil and climatic conditi- ons. The collected data includes length of life, first calving, milk yield, fodder regime, state of health of the different dairy herds and data on manure management and fodder production as well as soil and soil management data. Options to increase sustainability in the farming sys- tems are discussed with a special view to GHG emissions. Modelling of GHG emissions and weak point analyses in production shall be undertaken with the models GAS-EM and RE- PRO. General differences between organic and conventional dairy farming affecting the GHG balance can be expected by different milk production per cow, different feed components and obligatory grazing in organic farms and different GHG balances in the production of fodder crops. An increase in milk yields by a general intensification of feeding might be connected with unwanted effects on the GHG balance. Also, overall effects of the use of CH 4 -reducing