Today, agriculture has serious impacts on the health of our planet and its people. Humans are using the equivalent of 1.6 Earths’ worth of natural resources, which is already having detrimental consequences for ecosystems and biodiversity. In the context of these stresses, it is necessary to reexamine and redesign how biomass (living material made from plants) is produced. Humans rely on biomass not just for food but as a critical input for materials, clothing, paper products, and more. Responsible sourcing requires supporting a system of greater transparency, understanding, and continuous improvement in order to build healthier and more resilient farms, communities, and habitats.
Currently, agricultural practices often threaten critical ecosystem services – the services nature provides us like clean water, flood protection, and healthy soil – that act as buffers and offer protection against a changing climate as well as provide the resources our global economy needs to function and maintain food security. Changing the way in which the world manages and produces biomass is an enormous task and a difficult one – there are many daunting issues to tackle, and they vary greatly across different geographies.
For years, to advance its conservation mission, World Wildlife Fund has been helping companies understand the environmental and social risks of sourcing different crops. However, we saw the need for a tool to help companies bridge the gap between knowing that supply chain sustainability risks exist and then doing something about them. That’s what inspired us to develop the SRI, a new, open access online tool that is designed to make the sustainable sourcing process clearer, easier, and more streamlined. The SRI provides guiding questions in the form of a simple yes/no survey, as well as additional resources to help companies gather more information and build knowledge of how their supply chains are connected to global sustainability challenges. It also provides guidance on meaningful next steps – bridging the gap between awareness and action.
Many companies are wrestling with the challenge of moving from a general understanding of the risks and impacts inherent in sourcing biomass to addressing the most pressing issues in their supply chains. How do you know which questions to ask or what to prioritize? Knowing where to start isn’t easy – especially when comparing across many regions and production systems with different sustainability issues, ranging from labor rights to natural habitat conversion. The Supply Risk Inquiry provides a systematic way to begin answering those questions.
The SRI enables collaboration between organizations on responsible sourcing of biomass, leading to more informed decision-making. Although there are many challenges associated with the production and sourcing of biomass, together we can work to maximize positive outcomes for people and the planet.
Most anaerobic digestion plant owners consider their digestate (i. e. the solid and liquid AD Plant output) to be no more useful than for spreading on their fields, so here are 16 real uses for Biogas Digestate reported by WRAP. Some, such as food waste AD plant operators, may actually see it as a liability. But, when regulatory compliance and marketing are done right, biogas digestate has far more uses than you ever imagined.
Market a product for some of these uses for biogas digestate, and we think that there is a BIG potential for profit. So, keep reading (or watch the video below) this, and tell us if at the end, if you don’t then agree that biogas digestate is exciting!
1 Home garden products
A number of multi-purpose garden composts are available.
Composts produced from separated digestate fibre would provide a use for biogas digestate, which is a similar source of stabilised organic matter suitable for improving soil properties.
If mixed with woodchips, sawdust or straw the C:N ratio could be optimised, and replace the use of unsustainable peat-based media. However, some supplementing with added P and K, may be needed.
2 Horticulture: Landscaping
Digestate fibre courtesy Aikan Technology, via YouTube Creative Commons Licence.
Co-composted separated fibre would provide an excellent source of organic matter to use in manufactured soils for landscaping and is the second of our uses for biogas digestate.
3 Horticulture: Commercial fruit and vegetable production
PAS100 green compost is used for mulching of apple trees. Therefore, composted separated fibre from digestate could be used for a similar purpose.
4 Horticulture: Compost teas
The use of compost teas in the production of a wide range crops has become popular in the UK. This involves use of a ‘broth’ of microorganisms such as fungi, nematodes, bacteria and protozoa to improve soil ecology and hence soil health, productivity and plant health.
Digestate separated fibre could potentially be used as a feedstock for the composting process from which compost teas are produced. So, for use in making compost teas is another of our listed uses for biogas digestate.
5 Horticulture: mushroom growing media
Digestate may find it hard to compete with animal manures as the N and C were less available.
However, there is a large market and the mushroom industry may actually be the largest user of composted organics in the UK.
6 Horticulture: A fertiliser for commercial nurseries and herbaceous shrubs
Digestate fibre courtesy Vanderhaak biogas, via YouTube Creative Commons Licence.
Separated liquor would be more suitable than digestate fibre due to greater ease of infiltration into the soil giving more efficient use of nutrients.
However, supplemental P and K would be required so digestate liquor is not ideally suited to this purpose.
Demand can be anticipated for digestate fertilisers, compost and some mulch in ‘urban forestry’ or tree planting for landscape and amenity purposes, notably on brownfield land.
8 Use on publicly owned flower beds and green spaces
There is potential for composted separated digestate fibre to be used as a bedding material in publicly owned parks and gardens and for mulching trees.
Separated liquor may be useful as a turf fertiliser, subject to considerations regarding odour.
End of Part 1 – Now watch Part 2 of our article and our second video below, for 8 even more surprising, exciting, potential uses for Biogas Digestate.
Much of the public discussion around climate change has focused on how much the Earth will warm over the coming century. But climate change is not limited just to temperature; how precipitation – both rain and snow – changes will also have an impact on the global population.
While the models used by climate scientists generally agree on how different parts of the Earth will warm, there is much less agreement about where and how precipitation will change.
In the fifth and final article in our week-long climate modelling series, Carbon Brief explores where the models agree and disagree about future changes in precipitation.
Move evaporation and more water vapour
There are some basic physical processes that inform scientists’ expectations of how precipitation will respond in a warming world. With higher temperatures comes greater evaporation and surface drying, potentially contributing to the intensity and duration of drought.
However, as the air warms its water-holding capacity increases, particularly over the oceans. According to the Clausius-Clapeyron equation, the air can generally hold around 7% more moisture for every 1C of temperature rise. As such, a world that is around 4C warmer than the pre-industrial era would have around 28% more water vapour in the atmosphere.
RCP8.5: The RCPs (Representative Concentration Pathways) are scenarios of future concentrations of greenhouse gases and other forcings. RCP8.5 is a scenario of “comparatively high greenhouse gas emissions“ brought about by rapid population growth, high energy demand, fossil fuel dominance and an absence of climate change policies. This “business as usual” scenario is the highest of the four RCPs and sees atmospheric CO2 rise to around 935ppm by 2100, equivalent to 1,370ppm once other forcings are included (in CO2e). The likely range of global temperatures by 2100 for RCP8.5 is 4.0-6.1C above pre-industrial levels.
RCP8.5: The RCPs (Representative Concentration Pathways) are scenarios of future concentrations of greenhouse gases and other forcings. RCP8.5 is a scenario of “comparatively high greenhouse gas emissions“ brought about by rapid population growth,… Read More
But this increased moisture will not fall evenly across the planet. Some areas will see increased precipitation, while other areas are expected to see less due to shifting weather patterns and other factors.
The figure below shows projected percentage change in precipitation between the current climate (represented by the 1981-2000 average) and the end of the century (2081-2100) in the average of all of the climate models featured in in the latest Intergovernmental Panel on Climate Change (IPCC) report (CMIP5), using the high-end warming scenario (RCP8.5).
Purple colors show areas where precipitation will increase, while orange areas indicate less future rain and snow.
CMIP5 RCP8.5 multimodel average percent change in total precipitation (rain and snow) between 1981-2000 and 2081-2100. Uses one run for each model, 38 models total. Data from KNMI Climate Explorer; map by Carbon Brief.
On average, warming is expected to result in dry areas becoming drier and wet areas becoming wetter, especially in mid- and high-latitude areas. (This is not always true over land, however, where the effects of warming are a bit more complex.)
The average of the models shows large increases in precipitation near the equator, particularly in the Pacific Ocean. They also show more precipitation in the Arctic and Antarctic, where cold temperatures currently limit how much water vapour the air can hold.
The Mediterranean region is expected to have around 20% less precipitation by 2100 in an RCP8.5 world, with similar reductions also found in southern Africa. Western Australia, Chile, and Central America/Mexico may all become around 10% drier.
RCP2.6: The RCPs (Representative Concentration Pathways) are scenarios of future concentrations of greenhouse gases and other forcings. RCP2.6 (also sometimes referred to as “RCP3-PD”) is a “peak and decline” scenario where stringent mitigation and carbon dioxide removal technologies mean atmospheric CO2 concentration peaks and then falls during this century. By 2100, CO2 levels increase to around 420ppm – around 20ppm above current levels – equivalent to 475ppm once other forcings are included (in CO2e). By 2100, global temperatures are likely to rise by 1.3-1.9C above pre-industrial levels.
RCP2.6: The RCPs (Representative Concentration Pathways) are scenarios of future concentrations of greenhouse gases and other forcings. RCP2.6 (also sometimes referred to as “RCP3-PD”) is a “peak and decline” scenario where stringent mitigation… Read More
These changes tend to increase proportionately with warming; if the Earth warmed only 2C in an aggressive mitigation scenario such as RCP2.6 rather than 4C, the percent change in precipitation would be roughly half as large.
However, the simple picture painted by the average of all the models shown above hides profound differences. There are actually relatively few areas that all the models agree will become wetter or drier. Climate models are not perfect and projections of future average precipitation changes may become more consistent as models continue to improve.
There are 39 different climate models within CMIP5 that provide estimates of precipitation changes in the future. Unlike for temperature, where models show a general degree of agreement about future regional changes, different models may have the same region becoming much wetter or much drier in a warming world.
The figure below shows expected percent change in precipitation between the current climate and the end of the century in Australia, with purple areas indicating increased precipitation and orange indicating reductions. While the average of all the models – shown on the left – has a modest 5 to 10% reduction in precipitation over most of the country, some individual models show much greater changes.
For example, the Australian CSIRO model – middle panel – projects precipitation decreases of around 50% on average by the end of the century. In stark contrast, the Chinese FGOALS model projects a 30% average increase in precipitation by 2100, with almost no areas experiencing less rainfall.
CMIP5 RCP8.5 multimodel mean percent change in total precipitation (rain and snow) between 1981-2000 and 2081-2100 for Australia, as well as individual CSIRO-Mk3 and FGOALS runs. Data from KNMI Climate Explorer; maps by Carbon Brief.
Similar results can be found for many other regions of the world. The figure below shows the driest projection and wettest projections for each different part of the world across all the CMIP5 models, represented by the 10th and 90th percentile of all the models (e.g. the 10% of models that show the most reduction in precipitation and the 10% that show the most increase in precipitation for any region of the world).
In at least one model much of the world outside high-latitude areas and the tropical oceans shows sizable drying. Similarly, you can find at least one model where nearly any given location in the world gets wetter.
RCP8.5 10th percentile of mean precipitation change (left map) and 90th percentile (right map) for total precipitation (rain and snow) for each 1×1 latitude/longitude gridcell between 1981-2000 and 2081-2100. Uses one run for each model, 38 models total. Data from KNMI Climate Explorer; maps by Carbon Brief.
This means that average annual precipitation projections by climate models should be approached cautiously. This creates a challenge decision-makers who need to plan for changes that will occur in their country, as relying on the output of any one model may mask dramatic disagreements.
However, disagreements between the models in future precipitation changes in some regions does not mean that the models are useless for this purpose.
Where do models agree?
While models disagree on how average precipitation will change in many parts of the world, there are some areas where nearly all the models tell the same story about future changes.
The figure below shows the same annual average change in precipitation between today and the end of the century, but adds dots to indicate areas where at least nine out of 10 models agree on the direction of change.
As first figure, but with areas where 90% of the models agree on the sign of the change highlighted with dots. Data from KNMI Climate Explorer; map by Carbon Brief.
Here there is widespread agreement among the models that both the tropical Pacific and high-latitude areas will have more precipitation in the future. India, Bangladesh and Myanmar will all become wetter, as will much of northern China.
The models largely agree that the Mediterranean region and southern Africa will have less precipitation in the future. They also agree on reduced precipitation in southwest Australia around Perth, in southern Chile, the west coast of Mexico and over much of the tropical and subtropical Atlantic ocean.
Interestingly, despite all the focus on drought in the state of California, there is no consensus among climate models that the region will experience less precipitation on average in a warmer world.
Different changes in different seasons
A limitation of looking at annual precipitation changes is that they can mask some seasonal effects.
The figure below shows projected changes in future precipitation broken down by season, along with dots in regions where at least nine out of 10 of models agree on the direction of the change for each season.
A few things stand out when looking at projected seasonal changes. In winter there are greater reductions in precipitation projected over northern Africa, but no agreement on increases in precipitation over India or much of South Asia.
In spring, models agree that southern California will experience less rainfall. In summer, reductions in precipitation in southern Africa are particularly strong, while in autumn increases in rainfall over India, Bangladesh and the Sahara region all stand out.
Increases in extreme precipitation
Models also generally agree that precipitation, when it does occur, will become more intense nearly everywhere. Unlike average annual precipitation, almost the entire world is expected to see an increase in extreme precipitation as it warms.
Models suggest most of the world will have a 16-24% increase in heavy precipitation intensity by 2100. In other, words, heavy rain is likely to get heavier.
You can see this in the figure below. Here percent changes in heavy precipitation events by the end of the century are shown per degree warming that we experience, and dots represent areas of the map where 90% of the models agree. Red areas show decreases in heavy precipitation, while blue areas indicate increases.
The largest increases in heavy precipitation events on land are expected to occur over central Africa and South Asia. On the other hand, North Africa, Australia, Southern Africa, and Central America may not see a noticeable increase in heavy precipitation.
Percent change in heavy precipitation per degree warming, defined as the heaviest daily precipitation event of the year for each location. Figure adapted from Fischer et al 2014.
Temperature and precipitation influence drought
While changes in rainfall and snow in a warming world are highly uncertain for many parts of the world, changes in future precipitation are only part of the story.
Just as important is temperature, which influences whether precipitation takes the form of snow or rain and controls how much “snowpack” accumulates.
The snowpack is the snow that accumulates in mountains during winter and provides fresh water to the valleys below as it melts in spring and summer. It is an important contributor to many rivers, and impacts river flow and water availability for agriculture, particularly in regions, such as California, where precipitation is concentrated in winter.
Temperatures also impact the rate of evaporation, with higher temperatures leading to faster soil moisture loss and an increased need for irrigation in agriculture.
This means that, even for regions that are likely to get wetter, this will be largely offset by temperature-driven drying.
As Dr Benjamin Cook at the NASA Goddard Institute for Space Studies tells Carbon Brief, while changes in future precipitation is uncertain, the drying associated with warmer temperatures is much more widespread:
“The drought-climate change story is actually pretty complicated. While the impact of climate change on precipitation is fairly uncertain, we do expect with warming that many areas will experience more soil moisture droughts and declining runoff and streamflow resulting in an overall increase in drought risk and severity.
“The general consensus is that precipitation will decline in subtropical regions, places like the [US] Southwest and the Mediterranean. But the warming effect and impact of warming on evapotranspiration and associated drying happens over a much, much larger region.”
Changes in average precipitation is much more difficult for climate models to predict than temperature. There are many parts of the world where models disagree whether there will be more or less rain and snow in the future. However, there are some regions, particularly the Mediterranean and southern Africa, where nearly all models suggest rainfall will decrease. Similarly, increases in rainfall are expected in high latitude areas, as well as much of South Asia.
There is much more agreement by the models that a warming climate will increase the severity of extreme rainfall and snowfall almost everywhere. A warmer world will, they project, also increase soil evaporation and reduce snowpack, exacerbating droughts even in the absence of reduced precipitation.