Bio-based Building, Zuid-Holland

Commissioned by the Province of Zuid-Holland, BOOM Landscape studied the potential to cultivate bio-based materials in the region. The need for 210,000 new homes in the province over the next 20 years sparked this investigation. Environmentally friendly building practices are becoming increasingly important, certainly given the rising awareness of unfriendly conventional practices. Our report shows how the province can generate its own bio-based building materials by way of landscape transformation – a transformation that simultaneously addresses the alarming environmental challenges facing the area.

Landscape in crisis

That transformation is necessary is evidenced by the terrible state of large areas of ground in Zuid-Holland, as a result of current production practices. Parts of the landscape are sinking, subsiding, silting up, slaking, or becoming overgrown; CO₂ is being emitted instead of contained and rainwater is being pumped directly out to sea rather than being stored and recycled. For the most vulnerable areas, transforming the land into one of climate-neutral resources is an excellent alternative.

Reviving old landscape features

So what needs to be cultivated? The peat, sand and clay grounds of Zuid-Holland do not, in any case, lend themselves to large-scale forestry. To answer this question we looked into how the landscape was traditionally designed and managed, and which trees and crops supported this. By reintroducing old landscape features, the impoverished grounds can be rejuvenated and produce a rich and varied landscape full of natural and sustainable resources. Drawing on the best aspects of the past, we can also add to the production value by using modern technology which allows us to use old crops in new ways. Flax, for example, can be used to make insulation material now and not just rope.

Peat soil

Large swaths of peatlands are sinking due to oxidation and they are emitting high doses of greenhouse gases that damage the environment. We can combat this problem by redesigning the landscape to include marshes, wetlands, grasslands, and wild reed beds. This combination produces a rich biodiversity and a variety of water containment opportunities. Buffer zones around nature reserves help to contain water and to conserve water quality and, in combination with water-based agriculture, this will reduce soil desiccation. These interventions will turn the peatlands from sinking ecological deserts into a useful, sustainable sponge.

Sandy soil (Natura 2000 and NNN Landscape policies)

Intensive farming in the (calcite-poor) sandy soils of coastal regions requires a lot of pesticides and fertiliser. This contaminates the soil and surface water. Inland agricultural land also releases ammonium sulphate that flows down the rivers into the sea which then vaporises into nitrogen and settles on the dunes. Furthermore, nitrogen emission by farming, traffic, and urbanisation triggers the growth of more nitrogen-loving plants. In the context of sandy soils low in calcite, this will ultimately dry out the land and nature can no longer survive. The plan is to organise the sandy grounds into zones: in other words, an estate separated into wet and dry areas to cultivate forests and coppice woodlands, as well as dune valleys and seepage zones. Such an estate generates useful woods, meets the ecological needs stipulated by Natura 2000 and the NNN, and on top of this, is capable of absorbing CO₂, ammonium sulphate, and nitrogen.

Clay soil

Intensive arable and dairy farming has heavily salinized, compacted, and exhausted the clay soil.  Soil quality is harmed by over-fertilisation and the lack of variation in the farming. Compaction occurs with the use of heavy machinery and on account of the ever-increasing shortage of organic substances. Finally, soil salinization has become a serious problem – due in part to the effects of climate change. The groundwater of the low-lying polders is becoming infused with saltwater, and when the rivers are low and/or the sea is high, saltwater from the sea enters the internal waterways. This is causing an ever-increasing shortage of fresh water in the region.

To stop the damage to agricultural lands, the landscape needs to adapt to new functions. This will involve, for example, turning one area into a buffer zone for fresh water and another into farming that harvests crops more tolerant to saline soil. Seaweed is such a crop, and can be used as fireproof insulation material.

Healthy building, healthy future    

The cultivation of bio-based building materials generates many benefits. Their production generates less pollution, these crops absorb atmospheric aerosol particles, greenhouse gases and CO₂, the ground is able to retain more rainwater, and the new environments increase biodiversity. In turn, all this creates a better environment for business and a healthier, more attractive environment to live in. And homes that make use of these building materials fit more naturally into the environment, and will likely meet with less local resistance.